Return to the Building a Home Forum | Post a Follow-Up

 o
kitchen vent make-up air advice needed please (cross post)

Posted by threeapples (My Page) on
Tue, Nov 6, 12 at 20:48

we have three furnaces and three air conditioners and a 1200 cfm vent-a-hood in the kitchen. our kitchen designer is smartly suggesting we look into obtaining make-up air for when we turn the hood on high. the hvac guy says we need to spend $10,000 for a 4th unit just for this make-up air. we cannot afford another unit at this price, but are unsure what other options we have for this. opening the window is a possibility, but i don't want to forget to do that and have an issue. thanks


Follow-Up Postings:

 o
RE: kitchen vent make-up air advice needed please (cross post)

Yes, you need an ERV in your climate. This should have been planned all along by your architect and HVAC contractor. You are not likely to pass inspection without it.

The only other option would be to change over to a consumer grade range with a consumer grade 300CFM hood to match.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I have no idea what an ERV is, but our architect did not spec any HVAC so my husband, the builder, and the HVAC guy figured it all out together. The HVAC guy made no comment about make-up air--we just learned about it from the kitchen designer. We have a consumer grade range and it's on its way. The kitchen was designed around it and we cannot change it now. Had I known about this I would have mentioned it earlier, but it was just brought to my attention.


 o
RE: kitchen vent make-up air advice needed please (cross post)

It is very common for the architect not to have included the HVAC. What did your GC or HVAC sub do to determine what size system you needed? Your best bet would be to take your questions over to the HVAC forum.

Here is a link that might be useful: GardenWeb HVAC forum


 o
RE: kitchen vent make-up air advice needed please (cross post)

I think there is a much more affordable way to have make up air, although heated make up air (which you likely need given your climate) is more expensive.

I doubt opening a window will pass code . . .


 o
RE: kitchen vent make-up air advice needed please (cross post)

An Energy Recovery Ventilator is a continuous fresh air ventilation system so it cannot supply makeup air to a large capacity intermittent kitchen range exhaust since running the exhaust air through the ERV is not a good idea even if the ERV could have such a capacity.

You can run the range hood exhaust fan at the lowest speed and open a window when it is running at a higher speed or install a thru-the-wall makeup air grille somewhere that can heat the incoming air when necessary.

The link below will explain the issues involved.

Here is a link that might be useful: makeup air for range hoods


 o
RE: kitchen vent make-up air advice needed please (cross post)

I am familiar with exhaust air requirements for cooking equipment in commercial kitchens but I don't know of any requirements for exhaust air for a range in a residential kitchen.

However, make up air is regulated by certain residential codes in order to prevent backdrafting of combustion type heating equipment which can be extremely dangerous.

ASHRAE limits the total CFM of all residential exhaust fans to 15 cfm per 100 square feet of occupiable space, unless a backdrafting test is performed. It is very doubtful that a 1,200 CFM range hood plus bath exhausts, etc. would allow such a test to be successful. Any HVAC designer would know this but unless that designer is told the size of the exhaust fans make up air might get overlooked.

If the 2009 IRC applies, it requires exhaust hood systems of 400 cfm and greater to have makeup air equal to the exhaust air and to automatically open and close with the operation of the fan. This rule seems to be in response to the use of unusually large quasi-commercial range hoods.

Makeup air can be one of the casualties of splitting the responsibility for the design of a house between several parties with coordination left to the owner homeowner who might not realize the importance of certain information.


 o
RE: kitchen vent make-up air advice needed please (cross post)

See this discussion for approaches to make-up air.

I'm still wondering what on earth one is cooking that requires a 1200 cfm exhaust hood. I had a 700 cfm unit on last home and it felt (and sounded) like a jet was warming up in the kitchen. (Next time, I'm mounting an outside motor.)


 o
RE: kitchen vent make-up air advice needed please (cross post)

I used the kit linked below. We installed the inlet underneath the range. With this configuration the unconditioned air is nearly a non-issue.

MUA

@Worthy -- where did you install the blower. We have no audible motor sound in the kitchen from our attic mounted 1300 cfm blower (only the sound of air rushing over the baffles).

My inspiration: http://www.youtube.com/watch?v=NsSvMB9bJeE

Here is a link that might be useful: EuroStoves MUA kit


 o
RE: kitchen vent make-up air advice needed please (cross post)

We have no audible sound from our blower (attic mounted) 1200 CFM. We do need it when we use the charbroiler on our Wolf range - otherwise we set off the smoke detector!

Ingenious make up air solution wallyden!


 o
RE: kitchen vent make-up air advice needed please (cross post)

We have a Broan-like system for our 1200 CFM modernaire. I believe our builder charged us like $700 or something for the parts and installation. It's sort of hard to tell if this sort of thing actually works, except that we haven't died or set off the carbon monoxide detectors yet. No appreciable draft (it goes into our furnace return) but we haven't tested it at super low temps yet.

But I haven't found much reason to run the fan on 1200, especially for a long period of time, so I guess I haven't really stressed it yet.


 o
RE: kitchen vent make-up air advice needed please (cross post)

@Worthy -- where did you install the blower

The motor was integral with the fan and I had no idea there were alternatives. Live and learn.

Mrs. worthy is addicted to Jamaican cuisine--saltwater fish, tripe, curries, spices, goat, oxtail etc.--so hood exhaust fans are used a lot.


 o
RE: kitchen vent make-up air advice needed please (cross post)

This is such a !@#$% subject to me. I went round and round and finally bought a Broan Universal Make up air kit off Amazon (Cheapest) My HVAC guy is installing the actual duct pipes which
I bought online after no one helped me figure this out. I am using a Zephyr range hood 715 CFM and The Broan will duct into my air return in the basement
All together I paid around 1600$ and My DH will install and build the exterior of the hood
Wish us luck.
No one was much help at all on this not kitchen designers ( decided to not use one) Appliance sales people, The HVAC guy "just dont go higher than 400 CFM" The inspector requires it but had no guidance.


 o
RE: kitchen vent make-up air advice needed please (cross post)

my husband thinks he can do this himself and then we'll need a hole cut into our brick to vent to the exterior. i hate the idea of cutting a hole in the side of the house, but it sounds like there is no other way?


 o
RE: kitchen vent make-up air advice needed please (cross post)

We have a Broan MD6T motorized damper assembly on a Zephyr 720 cfm range hood. Instead of having the hole in the floor under the range as whallyden did, our is under the refrigerator in order to pre-condition the air.


 o
RE: kitchen vent make-up air advice needed please (cross post)

If you search the entire site you will find that this topic has been discussed many times and in great detail.

Installing a MUA duct in the floor of the kitchen works great for the short time you run your exhaust hood but for the rest of the time it wastes heat unless there is an automatic damper that closes when the hood is turned off. Such an intake should be well protected from entry by rodents.

Here is a link that might be useful: past discussion


 o
RE: kitchen vent make-up air advice needed please (cross post)

The Broan damper MD8TU instructions show the damper in another location from the kitchen attached via low voltage wire to the air sensor "finger" which is installed in the vent hood vertical exhaust pipe. Dont think it will work well in a horizontal.
The automatic damper is motorized and installs via ducting to your house return air vents then will be warmed with your house furnace.
This unit is meant for only using with a range hood as it only comes on when air is pushing the "finger" in the range hood vent.
For whole house MUA there are other more costly cha-ching units that of course warm the air.
This Broan unit is an inexpensive 200-300$ way to solve the MUA issue. April-Aire makes another but is more expensive. I bought the Broan on amazon.
This is something we will install when the range hood goes in.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Here it is

$207.50 at Amazon

Here is a link that might be useful: automatic MUA damper


 o
RE: kitchen vent make-up air advice needed please (cross post)

I just had mine disconnected today after being in our house a month :)

We went through this same thing. Only recently has our county started to enforce this, so our county inspector made us do it. However, that same insepector, our builder and our hvac guy said that with the size of our house (5500 on top 2 levels) that it's really overkill.

The code that Renovator8 mentioned "...2009 IRC applies, it requires exhaust hood systems of 400 cfm and greater to have makeup air equal to the exhaust air and to automatically open and close with the operation of the fan." is exactly what the inspector referenced.

If anyone is freaking out that I just disconnected mine, let me know bc hvac guy said he'd put it back on if I ever thought I wanted it. It just made this obnoxious noise, pulled in cold air from the outside and everyone thought it was overkill, so I had him disco it :)


 o
RE: kitchen vent make-up air advice needed please (cross post)

If you have other gas appliances or a fireplace, I hope you at least open the window when you turn on your fan. And re-connect it before you sell the house. The next homeowner may not know to do that to keep from killing the occupants with backdrafting carbon monoxide.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I am once again reminded of how inappropriate the term "overkill" is when applied to regulations that protect the lives of the public.


 o
RE: kitchen vent make-up air advice needed please (cross post)

As we understand it, our only options are to add another hvac unit (way too expensive), put a vent under the range, or out a vent in the wall! There has to be another way. Any ideas?


 o
RE: kitchen vent make-up air advice needed please (cross post)

Forgive me for pointing out the obvious, but another option (which would likely save money instead of costing more) would be to use a venthood that isn't 10x more powerful than a typical residential model. What do you cook that requires so much ventilation? I cook a lot, and I like to sear meat (lots of smoke), but I find my standard vent on high is perfectly adequate.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Zone4 - the manufacturer of the range usually recommends the CFM size. So technically not putting in an adequate sized fan would be a code violation.

I'd really like someone to run the stats on how many people have been killed by a Wolf range and running their hood without make up air. Anyone have a number other than zero? It takes using the wood fireplace at the same time and not noticing the smoke entering the room or a gas appliance in a living space. And even then, it would be hard in a large house to be a problem.

A alcohol sensor on every car ignition would save far more lives and not cost nearly as much.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I was just providing my recent experience for the OP. A mere knowledgeable recommendation rather then sarcasm would have sufficed.

Thank you david cary for pointing out what I also found to be the obvious on Wolf ranges/hoods and death rates. I live in Loudoun County/Northern Virginia. From 2003 - 2008 more mcmansions popped up here than probably anywhere in the country. The majority of these neighborhoods were filled with 48" ranges/powerful hoods...and gasp, no make up air. If they didn't foreclose on their house by now, I'm guessing they are probably still living there (key word - living).

If anyone in this post actually has one you'll know that the amount of make up air coming back into your home is extremely small. I truly get more air back in the house if I open the back door to the deck, and then instantly shut it. I'm not kidding. I can't figure out how this puff that comes back really does anything at all.

We installed the Broan system as well for this. It runs above the kitchen ceiling and out to the side of the house. The actual vent that puffs air back in is about 30 ft from the range/hood. I had the choice of putting this thing just about anywhere I wanted as long as it could link to the exterior wall.

I guess I should note that the thing my builder/hvac guy stated was if you were in a condo or smaller TH kitchen, yes, it may make a difference. But my kitchen is fairly large (at least 500 sq ft), and it's attached to a family room (about 400 sq ft) so it's doubtful when we use the hood for about 10 min every couple of days that we will die of carbon monoxide poisoining or anything else the magical make up air prevents. I mean, seriously people...if that were the case, don't you think Wolf and other hood vendors would have a huge CYA clauses all over their products by now??!

To my recollection threeapples has a fairly large home as well. My point was just to take the least expensive option bc in addition to the puff of air you'll get back, my hvac guy and the inspector both said they understand that this rule is up to be removed for residential homes of a certain size.

threeapples - take it for what it's worth. But, I wouldn't spend a lot of money on it. Ours ran about $700 for the broan solution/install, etc.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Not to mention that most residential codes require carbon monoxide detectors. Ours are hardwired and we have one on each level. . .

As far as the CFM requirement, Wolf does specify a 1200 CFM hood if you have a charbroiler, and it does make a huge difference. I have never charbroiled without it on high but have charbroiled without turning it on by mistake and it took about 2 seconds to set off the smoke alarms. . .


 o
RE: kitchen vent make-up air advice needed please (cross post)

"So technically not putting in an adequate sized fan would be a code violation."

I've never seen a national consensus code that required a residential cooking range to be vented or have an air exhaust system nor have I heard of a state or local code that required one. I have been told by several appliance salesmen that a hood was required by "code" for a large range but none of them could tell me where they got that information.

The 2009 IRC says: "Appliances not required to be vented. The following appliances shall not be required to be vented:

1. Ranges.

The WOLF VENTILATION GUIDE says:
"Wolf cooking products do not require ventilation when installed according to the installation instructions. Recommendations and suggestions in this guide are for performance only."

The GUIDE also says:
"Wolf prefers an HVAC contractor approve the airflow characteristics of any ventilation and duct work system."

As for the danger of backdrafting, I would never put a bedroom near a gas-fired heating system but many designers, including GardenWeb members, have no fear of doing that and/or rely on CO detectors to warn inhabitants.

As for building codes, they are not only concerned with the number of deaths attributed to a given condition, they are concerned with the health of the people most susceptable to CO: the elderly, infants and people with health problems.

Some research has found that repeated exposures to
CO, even at levels previously believed to be low, are capable of producing numerous, and persistent, adverse physical, cognitive, and emotional health effects in humans."

HUD's "HEALTHY HOMES INITIATIVE - Carbon Monoxide" says:
"Non-Fatal CO Poisoning. In addition to CO poisoning fatalities, it is estimated that thousands go to hospital emergency rooms for treatment of non-fatal CO poisoning each year... During 2001-2003, an estimated 15,200 persons with confirmed or possible non-fire-related CO exposure were treated annually in hospital emergency departments, with most (64%) of the nonfatal CO exposures occurring at home. Furthermore, some researchers suggest that CO poisoning commonly goes unreported or is medically misdiagnosed because symptoms can be easily mistaken for other illnesses such as the flu (Penney, 2000; Hampson, 2000; Comstock et al., 1999) and chronic fatigue syndrome (Knobeloch and Jackson, 1999).
Therefore, although there is no reliable method for estimating the number of individuals who suffer from symptoms of CO poisoning, it may be considerably larger than reported."

The issue is not what the code requires but how far you are willing to go to protect your family's health.


 o
RE: kitchen vent make-up air advice needed please (cross post)

The salesman for our 60" Wolf with a grill component said we needed this amount of cfm's for our hood. We heard the same from the cabinetmaker, the kitchen designer, and builder. Believe me, I'd love to not have such a large, noisy hood.
Andi, how large is the visible portion of the Biotin in your kitchen? What does the exterior vent look like?


 o
RE: kitchen vent make-up air advice needed please (cross post)

What are the model numbers of your range and hood?


 o
RE: kitchen vent make-up air advice needed please (cross post)

The vent moves enough air to completely replace *all* the air in a 3500 sq.ft. house in 30 minutes. It's not a small amount of air, even if you only run it for 10 minutes. Physics says that air must be replaced. If there's no make-up air vent, where is the air coming in? If it's not coming down the chimney, is there a seal somewhere that's broken? What else will come in there? We had a broken seal where our air conditioner compressor's power came into the house that became a rodent entrance.


 o
RE: kitchen vent make-up air advice needed please (cross post)

The tighter the house, the more important the make-up air becomes. If you live in a leaky house, then you probably won't have a problem. I'm betting making a tight, energy efficient house was not at the top of the list of requirements for those mcmansions.


 o
RE: kitchen vent make-up air advice needed please (cross post)

The 1200 CFM is in fact recommended for the Wolf with grill. For good reason I think. It is searingly hot (one temp) and anything with fat really really smokes.

I would highly recommend the remote blower kit for the fan. We have that installed in our attic and the fan makes little noise.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Athens, we have no way to do a remote blower because it would be difficult to access for maintenance. My husband says we can't do this easily with vent a hood


 o
RE: kitchen vent make-up air advice needed please (cross post)

The vast majority of CO exposure is on old houses for a variety of reasons particularly kerosene heaters. Sure CO happens, I'm just not sure that it ever happens in a modern home. So even if 1 million people went to the ER every year for CO poisoning, there still would likely be zero from a lack of make up air with a big range hood.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Just recieved the Jan 2013 Fine Homebuilding magazine today.
There is an excellent article on MUA for range hoods that will explain this better than anything I've read so far. There are pictures and diagrams, all you need to know. Believe me I've read it all!!! I'd link but its not on their website yet. (They feature a good kitchen island design article too)
My family had a serious near miss with CO poisoning when I was a child. Faulty propane furnace. I sleep with the window open year round because of it, much to my DH's dismay.
My inspector is savvy to all things venting and has reaaaaally pointed out all of the nuances of the code. Inspection is Tuesday. Wish me luck.
My HVAC guy said it wasnt CO from the range that was the issue it would be more of a backdraft of my wood burn FP sending ashes all over the house when the vent hood kicked in.


 o
RE: kitchen vent make-up air advice needed please (cross post)

ppbenn, i'm looking forward to that article going online. we will have two wood-burning fireplaces, one is a stove actually, so this is very interesting to me.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I have a 60"wolf range and have the standard 400 CFm blower. We don't have a grill but we do have the French burner. yes, the 1200 CFm blower was recommended but we did not want to deal with make up air. the 400 CFM has worked just fine- we've been in the house for over 2 years.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I have read some things about requirements for "400 cfm and over" and others about "400 cfm and under." If I'm not mistaken, I read both those sentences in the Fine Homebuilding article as well. (Which I was going to recommend, but someone beat me to it.) So what category is a 400 cfm fan? Does it require MUA or not?


 o
RE: kitchen vent make-up air advice needed please (cross post)

hi three apples....just saw your ? and I'll get pics today for you.


 o
RE: kitchen vent make-up air advice needed please (cross post)

lori - Here is the relevant section of the IRC

M1503.4 Makeup air required.
Exhaust hood systems capable of exhausting in excess of 400 cubic feet per minute (0.19 m3/s) shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Thanks, dekeoboe! That helps me. I have a lot more options if a 400 cfm fan is OK in my tight house. Maybe some day I will learn how to find and interpret things in those codes. Meanwhile, it is nice to have people I can ask!


 o
RE: kitchen vent make-up air advice needed please (cross post)

400 CFM is a pretty wimpy vent hood. There are OTR MW's that will vent to that capacity. It's barely adequate for even a consumer grade gas range. It's inadequate for a pro grade range.

With all new houses being built to energy standards that are many times tighter than something from the 50's would ever be, this requirement will only get more stringent. It would be the smart builder who educated themselves and got ahead of the requirements rather than merely trying to satisfy what the inspector will allow by the barest skin of his teeth.


 o
RE: kitchen vent make-up air advice needed please (cross post)

No problem lori. If your house is really tight, you might want make-up air even if you vent hood is only 400 cfm. This is especially true if you might be using other items that will be drawing air out of the house at the same time as you are using the vent hood. We have a very tight house, so we also have make-up air for our electric dryer.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I'm wondering if 400 cfm is "wimpy" for all circumstances, or just some? We will not have other combustion sources (having radiant heat in the floors, elec water heater, an energy recovery ventilator.) But the house will be as tight as we can make it. Planning on a 36" induction cooktop, and have read the rule of thumb suggesting 100 cfm per 12". I would think the way you cook could make that an over- or under- estimate. We don't tend to set our smoke alarms off the way we cook now. Smoky things tend to get done on the grill right outside the kitchen door, but we do stir-fry some. Our current "wimpy" hood seems to manage that just fine. We don't use it on the highest setting all that often. I will certainly be looking into this more in the coming months.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Oh, forgot to mention our laundry is in a separate building with its own exhaust fan.


 o
RE: kitchen vent make-up air advice needed please (cross post)

We haven't installed the 36" BS rangetop yet and we haven't found our perfect vent hood yet but... My heat/AC guy said we do not need to worry about make-up air because he put our two furnaces up in the attic and we have those "spinning" things on our roof. Has anyone heard this before?


 o
RE: kitchen vent make-up air advice needed please (cross post)

Having the furnace combustion in the attic doesn't remove the requirement for makeup air. It's not just about the other sources of combustion, it's about the overall air tightness of the home. You cannot suck air through a straw out of a jar unless there is another hole or holes in place to replace that air. You get nothing but a collapsing straw if you keep trying.

And I didn't think there was anyone still putting in turbines on a roof for ventilation. Vented soffits and a ridge vent have been the standard for over 10 years here, and we're not the most technologically forward location in the country.

I think you may have other issues in your build beyond makeup air given the uneducated statements that your HVAC person has made here and the building practices done by your contractor.


 o
RE: kitchen vent make-up air advice needed please (cross post)

We are in the middle of a conversation with our HVAC and GC about an ERV that was specified by the architect in response to my husband's request that we be able to get fresh, clean and filtered air into the house without opening windows and letting in dust and pollen. (Lots of allergies). The HVAC guy is proposing a RenewAire EV90 which has 90cfm and tempers the air. He can put it so the fresh air is ducted into the return plenum of the AC airhandler or have it just stand alone, independent of the system. We can't evaluate his proposals. We are having hydronic radiant floor heat partly because I hate forced air (noise and breeze) and don't want to have to run the air handler just to get the fresh air distributed. In addition, we have 3 powerful bathroom vents (190 in the master and guest bath and 130 in the powder room). Obviously we won't use them all at the same time unless we have a lot of guests, but we have adequate ways to exhaust, just not adequate ways to get fresh and make up air in. This is all before I choose my range hood and vent. I was figuring on a 400 cfm unit but may downsize just to avoid the make up issue. I will have a 36" induction range. Heat and fireplace are propane. i don't really understand the issues but want to take the time to get it right. Contractor and HVAC guy don't seem to want to figure out the solution - just get something installed so they can get paid and on to the next job. I desperately need some advice! Thanks for any opinions. P.S. We are in the final month or 2 of our new house building so this is not the time to change contractors.:(


 o
RE: kitchen vent make-up air advice needed please (cross post)

ellessebee, an ERV is for energy recovery in a fresh air ventilation system and it would run full time so it should just dump tempered fresh air into the house at some central location or in a limited distribution pattern.

This fresh air ventilation system is independent of any make-up air for the exhaust fans in the house. If the kitchen range hood draws excessive air it could create a negative pressure in the house and carbon monoxide and other by-products could be drawn into the house from your hydronic boiler.

Ask your designer to put the boiler in a separate room with a CO detector with a dampered combustion air intake in the exterior wall that can accommodate changes in interior air pressure. Since the outside air will be drawn through the firebox and up the chimney it might not need to be heated.

But relax, there will be code required interconnected hardwired CO detectors near your bedrooms in case all of the windows are closed and someone wants to run all of the bath and kitchen exhaust fans at full speed all night long.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Thanks, Renovator8. I'm coming to realize that I've confused the issues. We originally just wanted to get clean, fresh air into the house without opening windows. That's what the EV90 is about although we don't know if it's preferable to duct it into the AC air handler that I don't want to run much or just let it flow into the house on its own steam. But after reading the related threads on this site I'm seeing that we REALLY need to be concerned about makeup air for the bathroom vents, range hood vent, central vac and clothes dryer that will all suck air out of the house. Without clean replacement air, we will be sucking from the attic and up from the basement (dusty and full of fiberglass particles), the flue, or just in from the outside through any leaks in the building envelope - defeating our purpose of wanting to bring in filtered air as much as possible. Obviously we could just open a window when we run these appliances, but we were hoping for some device that would be filtered and have a heat exchanger - but not necessarily with its own exhaust since we have plenty of exhausting appliances already to make up for. So it's not just CO we're worried about. We're wondering now if we have the EV90 connected to the air handler (return) but don't turn on the air handler would the fresh air be drawn into the house through it when we run another exhaust fan(s) elsewhere in the house? Or is there another kind of device meant to do what we want? Thanks.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Our builder advised us to just open our kitchen window when we have our hood on high, which will likely not happen often. I guess we'll see about passing inspection soon enough. I'll keep you all posted about what the inspector has to say about this issue in our kitchen when we reach that point.


 o
RE: kitchen vent make-up air advice needed please (cross post)

The RenewAire EV90 has a very low airflow of 40 to 110 cfm and would only be able to supply fresh air for a small house or apartment. It is typically used as a substitute for a bathroom exhaust fan. It can be run from a manual switch when needed or on a timer for a percentage of each hour. Filtration is another issue. It can be wired to activate a furnace blower for air filtration.


 o
RE: kitchen vent make-up air advice needed please (cross post)

We've only recently learned that about the EV90. The HVAC guy didn't suggest using it in place of a bathroom fan, unfortunately, and we just bought 3 new and more powerful ones. Clearly the EV90 won't do what we want. In all fairness to the HVAC guy, we didn't understand the make-up air issues when we started out - but he didn't say anything about it either. We thought we just wanted a way to get fresh air in without losing heat from time to time - our radiant system can't recover quickly from an open window or door and we wanted a filter to keep pollen and dust out. Now we have an abundance of exhaust fans but no way to make up for them. That's what we need now. Maybe some kind of port with a filter and heater that's triggered by pressure or electronically or even manually when we turn on one of the fans? SOmething like the intake side of the EV90 without the exhaust part. Mostly we'd be using the bathroom vents. The kitchen vent less often. We'd only need the heater in the winter. We don't need to draw in fresh air round the clock - only as needed. Our AC unit will be able to compensate in the warmer months for the loss of conditioned air. Does such a device exist or can it be fabricated easily? We're in NY, by the way, not a warm climate but not as cold as they come, either. Thanks for sharing your expertise - invaluable!


 o
RE: kitchen vent make-up air advice needed please (cross post)

There are whole house filtered heat exchange units.

Here is a link that might be useful: BROAN HEPA air exchanger


 o
also

There are special make-up air units.

I don't know how these products would work with your hybrid HVAC system.

I suggest you start over with a qualified HVAC designer rather than cobble together something that could cause trouble later and for which no one will accept responsibility.

Here is a link that might be useful: Make-up Air and Combustion Air Diffuser


 o
RE: kitchen vent make-up air advice needed please (cross post)

It's too late to start over but I would be thrilled to have a knowledgeable HVAC designer step in and pick up at this point - except I can't find one. When I search for HVAC contractors in the area, none talk about ventilation - only heat and AC. All of our AC equipment is already in place as are the bathroom vents. I haven't purchased the kitchen vent yet. Since we're not yet living there (although the sheetrock is up) we can still go through walls and there are placed in the attic and eaves where we can run ducts. I am sure a smart designer could figure it out but I can't find one! Thanks for your recommendations. I will look into the Broan.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Isnt it neat how a seemingly silly requirement can lead to a better understanding of building science and the home as a system?

Its too bad that most people reading this thread have probably already made their beds for design options and using the right professionals to build their home.

Would also like to point out that cars left running in attached garages is another dangerous issue surrounding this requirement. Pulling air from crawlspaces, cracks in slabs, and vented attics is also very undesirable.

Those building a home that are concerned about these issues should build to current IECC energy codes and insist that the home conforms to ASHRAE 62.2 ventilation standards.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Yes, Brian, but even those of us who have not made our beds yet remain somewhat mystified about this topic. At least in our area, some of these requirements (new energy codes) are just now going into effect, so we are guinea pigs as the design pros figure it out. Or we add it to the list of things we need to research on our own! And it's a long list already...


 o
RE: kitchen vent make-up air advice needed please (cross post)

I've been making my bed for nearly 2 years now and not once along the arduous path of design and construction did any of the professionals I hired or consulted breathe a word about make-up air. I even attended several seminars on passive and zero energy design in an attempt to get myself better educated about energy efficiency and I never heard the word there, either. So how i was supposed to get a better understanding of building science than even my professionals have is beyond me! My HVAC contractor seems clueless even about an ERV and it's in the plans only because my husband is looking out for my allergies and wants me to have a fresh air intake during peak allergy season. Most of the time we prefer to open the windows. How do passive houses deal with cooking exhaust? Are they fabricating their own systems ad hoc? Why hasn't the ventilation industry read ASHRAE 62.2? I have combed the local area for a better, more knowledgeable HVAC contractor and there are NONE that list ventilation among their services. I am going to try commercial contractors. It's an awful feeling when you've been designing and building a house for 2 years and you're only a couple of months away from a C of O and you find you've overlooked something significant like this. It's even more awful when you realize you had professionals working for you whose job it was to make sure such things didn't happen. And now I'm the one who has to fix this....


 o
RE: kitchen vent make-up air advice needed please (cross post)

ellessebee, you seem to be lumping together vents, exhausts, fresh air ventilation and make-up air. The need for these systems must first be identified separately and then modified to work together and the responsibility for that work is often shared and therefore overlooked.

The building code for single-family houses requires mechanical ventilation (fresh air) only if each habitable room does not have operable windows with a minimum clear opening of 4% of the room floor area. If you want mechanical fresh air ventilation you need to tell the designer.

When your husband asked for fresh air to be mechanically introduced into the house it was necessary for an equal amount of air to be removed and that was done with an independent stand alone energy recovery unit that did not affect the interior house air pressure.

An oil or gas fired furnace or boiler and a gas fireplace vent does not remove much air from a house but negative pressure can prevent combustion gasses from rising by gravity up the vent but that can be avoided by supplying outside air to the equipment.

Make-up air would be required only if you have unusually large mechanical exhaust fans in the bathrooms and kitchen. The bathroom fans can have a built-in energy recovery feature that balances the exhaust air with incoming tempered fresh air.

Unfortunately, that can't be done with a range hood exhaust which is why this thread is about that subject. A range exhaust is required by code to have an automatically operating make-up air intake if it is over 400 CFM. Whether that is needed and how energy can be conserved is an issue no one has fully solved. The responsibility for the design of this equipment is often not clear between the trades and therefore the architect or GC must make that decision and make sure it gets done.


 o
RE: kitchen vent make-up air advice needed please (cross post)

This is a good thread with important discussion on a hot topic which I stumbled upon while searching MUA.

"The Broan damper MD8TU instructions show the damper in another location from the kitchen attached via low voltage wire to the air sensor "finger" which is installed in the vent hood vertical exhaust pipe."

We'll soon be installing the Broan MD8TU set up, running to exterior brick wall through a crawl space (not drawing through crawl space) next to furnace return.

My main question is: will someone in the know confirm that the low voltage power supply (transformer), being electronic as opposed to magnetic, should NOT interfere with nearby low voltage magnetic transformers utilized for under cabinet lighting (UCL)? I wish to minimize any risk of cross noise between these two adjacent low voltage systems and could use direct wire UCL if humming will occur due to two low voltage adjacent systems.

Also, for anyone who has an 8" exterior damper (which is big, wish I could do 6" instead), how did you seal it's exterior edges, with foam? What critter/insect cage did you put on it, and did you put in a 3M filter adjacent to it interiorly? Can you recommend a specific insect cage/filter system? I understand a filter may cut down on draw? Still, who wants insects in that ducting.

Andi_K: "my hvac guy and the inspector both said they understand that this rule is up to be removed for residential homes of a certain size". Any idea when? Nevermind for us, as its code now.


 o
RE: kitchen vent make-up air advice needed please (cross post)

We have the 6" one. We foamed where the ducting runs through the wall. And sealed the exterior hood flashing with silicone. We did not use an insect cage, just went with the mess that was included with the unit. We also did not use a filter.

We don't have low voltage lighting, so I can't help with that question.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I have a 30" Bluestar RNB304BV1 gas range with 22K burners (2) paired with a Broan E6030SS 30" 600CFM hood range. 7" ducting up and out the crawl space above the kitchen with one 45 bend.

I have Mitsubishi Electric heat pumps and ripped out my conventional 125K BTU furnance that never worked well.

I have a "regular" wood fireplace whose damper I just had replaced.

Last winter - the first with the new range, range hood, and electric heat - with the range hood on (even at the lowest fan speed 150cfm) and a fire going in the fireplace, smoke would pour into the living room if we didn't open up the backdoor screen in the kitchen. It didn't take very long to figure that out.

My house is a 1947 cape that is not "tight" by any means. It barely has any insulation in the walls at all.

In any case, it is very clear to me that I need a MUA solution as last winter was the first winter with the new setup.

I also live in NY which means I need the make up to be heated or else my wife is going to kill me. And I don't have the option to have the MUA directed to the return air of my furnace....since I don't have a furnace any longer.

I checked out the broan site and if you bring up the page for the MT8DU there is a MUA specifier (link below). It recommended that I install TWO of their 8" dampers! I think I'll give them a call next week to find out exactly why they suggest that. Although I must admit when filling out the form there were some parameters that I was not familiar with.

All of my old supply and return vents and vertical ducts are still in place except they have all been closed up with sheet metal and screws - thus easily opened up. I have a supply register just off the floor on the perpendicular wall 3 ft away from the range hood. I suppose I could run MUA from the outside, bring in cold air into the basement, but open the supply register that would bring up somewhat warmer existing air in the basement into the kitchen.

The flips side to that after experiencing the coldest winter of all time last winter is that it would just make the basement even colder than it already was (which was very, very cold). So....perhaps I need to heat it after all.

I'm curious dekeoboe as to how you determined you only needed one 6" MUA device when you have more CFMs exiting the range hood than I do.

Hm when I look back at this post it seems like it's not such a straightforward solution.

I could install the MUA device on the far perpendicular wall as I have space to run at least 5' of pipe for filtering and heating purposes. Running power to the location is no problem either as the basement ceiling is completely bare at the moment.

Opening a window when the range hood is on is neither code nor comfortable although it does solve the problem.

On a related note I do a lot of wok cooking and man with that 22K burner on the BlueStar I need the entire 600CFM. In hindsight I probably should have gone with a 36" hood instead of 30" but alas too late now.

Any suggestions on how to proceed? Lastly the budget needs to be as low as possible.

Here is a link that might be useful: Broan Make Up Air Specifier

This post was edited by lordoftheflies on Sat, Jun 28, 14 at 22:12


 o
RE: kitchen vent make-up air advice needed please (cross post)

This is an old thread. Make up air for hoods larger than 400 CFM are now required by the IRC to have make up air. But even a large system should not cost more than $1,000.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I understand that I require a MUA system. I'm not arguing that point. I'm confirming the fact that with a fireplace in winter that is in use I *must* have a MUA system in place.

What I'm looking for is advice as to how to get heated MUA into the kitchen without parting with too much $$$. And also trying to figure out exactly how much MUA I actually need.

My house is not huge. 2200 sq ft plus an unfinished basement (1000 sq ft).

Should I bring the MUA directly into the kitchen via a device like the Broan MT8DU about 15 feet away from the range?

Or should I bring it downstairs to the basement and open up an old central air supply register that is closer at about 4 feet away from the range?

Should I bring it into the wall of the adjacent dining room?

I imagine I would have to have it closer than the fireplace otherwise the negative pressure will relieve itself from the closest point as the damper will be open with the fireplace in use.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Perhaps something like this:

$780
700 cfm
10KW
240V
10" duct

http://ecomfort.com/em-wx1025r-electric-duct-heater-10kw-10-pipe-section-700cfm-240v-110.html

Here is a link that might be useful: EM-WX1025R Electric Duct Heater


 o
RE: kitchen vent make-up air advice needed please (cross post)

We have a 6" exhaust duct, so we went with the 6" size. We checked with our HVAC people and they said the 6" size was fine.

The tool that is on the Broan website did not exist when we built. The tool isn't the best anyways because it does not give you enough options. For example, there are only four choices for Exhaust Duct Length and Elbows and none of them cover our situation.


 o
RE: kitchen vent make-up air advice needed please (cross post)

Understood. Will post back after I speak to them. How is it working for you? I assume it is providing sufficient make up air. Do you have a fireplace that is in use during winter? How did you know you needed make up air?

Hm. It would seem that our ducting size is not exactly....accurate. I checked a couple of sites and it says that to be able to move 600CFM you need 12" round metal duct!

6" x 6" x 3.14 = 113.04 square inches.

600 CFM / 113.04 = 5.307 cfm per square in.

Using a 7" duct that means 3.5" x 3.5" x 3.14 = 38.5 square inches.

Thus 5.307 cfm per square inch x 38.5 square inches = 204 cfm in a 7" duct

Math from here:

http://hvac-talk.com/vbb/showthread.php?105192-CFM-s-per-duct-size

Here's another source that also suggest 12" round smooth duct to get to 600CFM.

www.virginiaair.com/index.php/contractors/documents/doc_download/475-residential-duct-sizing-guide

Here's a link from prolinerangehoods that says for a 401-600CFM range hood minimum is 6" and 8" is optimal. Also says that the smaller diameter duct results in the motor working a little harder thus shortening its life.

http://www.prolinerangehoods.com/1-801-973-3959/support/range-hood-duct-sizing-guide/

Of course all these numbers refer to 100' of duct which I have way less so I suppose that sort of works out in my favor slightly. I also am going straight up from the range hood and one 45 degree turn out to the roof cap.

Hm.


 o
RE: kitchen vent make-up air advice needed please (cross post)

The make-up air works great. No, we do not have a fireplace. We live in central NC and decided it would not be used often enough to justify putting one in. Winters like the last one had some days I was wishing for one though!

Our house is Passive House certified; it is very tight. We averaged .42 ACH at 50 Pa on the blower door test. We knew from the beginning we would need make-up air.


 o
RE: kitchen vent make-up air advice needed please (cross post)

So you have the Broan 6" MD6T and you have it unfiltered, unconditioned, and ouputting under the fridge for conditioning purposes? So you are relying on the exhaust heat of the fridge to cool the incoming air? How cold did it get this past winter for you? How cold was that make up air? Detectable at all? Here we had -20 real feel in NY with the wind chill at times. It was brutally cold and cold often. I think I might have to put in a heated MUA.

So update on Broan. The lady I spoke to today was completely useless. To make a long story short she had absolutely no idea how to use the Make Up Air Specifier on her site. It was quite pathetic and my impressions of Broan's customer service = suck.

I spoke to Dean at Electro Industries at length about all the factors I'm thinking about. We went over two options - one using the MA-10 (10kw all in one 10" heater with damper, blower, filter, and current detector to control blower speed) and the less expensive heater unit EM-WX1025R. The broan MD6T comes with a 24volt 20VA transformer so I could then use the one signal to turn on both the Broan damper and the heater unit.

Both options unit can accomodate up to 637cfm in a 50 degree temperature rise.

It's a 10kW unit though and would require a 50A or 60A two pole (240V) breaker and its own dedicated lines (of course). I can take care of the electrical so no problem there but man I'm guessing my heating bill (which was astronimical last year) will be more than I can tolerate this year.

Temperature Rise Needed/CFM
EM-WX1025R 10000 Watts

80/395 70/452 60/527 50/632 40/790 30/1054

MA-10 $1917 + freight
EM-WX1025R $800 + freight.
I think that should be sufficient - it's better to have 50 degree air coming in than 0 degree air.

I'm thinking that maybe I can get away with non-heated air if I can get fresh air to come up that old supply register near the range. The opening is closer than the fireplace but it might work if I put a blower in-line as well.


 o
RE: kitchen vent make-up air advice needed please (cross post)

I was searching for "does irc 2009 require make up air to be heated forum" and found this article that is basically exactly what I experienced today when speaking to Broan.

http://www.greenbuildingadvisor.com/blogs/dept/musings/makeup-air-range-hoods

How funny. They mention the exact 10kW unit I was talking about (although they listed their price as $1800!).


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Building a Home Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here