What are your current gas and electricity rates? This will help determine whether the change makes sense.

If you removed the duct work how will connect the heat pump? Are you thinking about installing a ductless mini split?

Hi, Mike,

Gas rates are difficult to figure out, so I am copying part of my bill, you probably will be much better at decifering it.

12/07/12 12/31/12 Basic Charge $8.08
12/07/12 12/31/12 Delivery Charge 133.95 Therms @$.3924 Per Therm $52.56
12/07/12 12/31/12 Cost of Gas 133.95 Therms @ $.56627 Per Therm $75.85
12/07/12 12/31/12 Gas Conservation Program Charge 133.95Therms @ $.01927 Per Therm $2.58
12/07/12 12/31/12 Merger Credit 133.95 Therms @ $.00368CR Per Therm $.49CR
12/07/12 12/31/12 Effect Of Lake Stevens City Tax $138.58 @ $.0551 Per Dollar $7.64

The electric rates are 0.08852 PerKWH.
I am not a in the business of installing or building, so I don't know what is "ductless mini split", and the question whether it makes sense from purely economic perspective does not apply here. I am willing to beare the cost of doing so if I can get rid of the mess under my house and gain access to the crawl space when I need to go there.
Whether it should be "ductless mini split" or some other type, that's the question that I am looking for answer to. Whatever would make sense in my situation:4 bedrooms, 2 living rooms, 2 story (I forgot to mention that detail: the addition is 2 story with 2 bedrooms, kitchen open to living room downstairs, the old part is 2 bedrooms and a living room, seldom used:holidays).

Google "ductless mini split" and you will get an idea. It is a small heat pump with a condenser outside and a unit which is mounted on the wall inside the house. The air flow comes from the inside unit. Your house would need several of these so I don't know how practical this solution would be.

Is it possible to relocate the furnace in order to minimize the duct work in the crawl space? What about re-routing the duct work so that you gain some additional space?

while we are asking questions...
can the ductwork be moved into conditioned space.
furring down hallways, along walls in rooms &
locating furnace inside a closet?
this would require some carpentry work,
but putting ducts & equipment inside the living
space is very efficient.
This is what I did, took some figuring out
but all ducts are inside the living space.

with hard pipe ducts (with missing duct wrap)
in crawlspace, it will be very costly to heat/cool.
the lack of insulation will make it
expensive & ideal for critters to take up
residence under your home.

you could put everything in the attic...but
thats not a good idea either as temps in
attics are extreme & insulation on ducts
is minimal.

what is your location?

is your floor plan open enough that minisplits
would work? or would you have to put the
minisplit air handler unit in every room?
that would be very expensive.

also, if you invest in a blower door
test & seal air leakage into the house
it will improve comfort & be easier to heat/cool.

could you make us a drawing of the layout
of your house both first & second floors?

is your crawlspace open?
have you gotten any opinions from
hvac compaines in your area?
ask about dual fuel heat pumps. keep the
gas but only use when temps are lower
than heat pump can handle.

lots of questions!
best of luck.

Yes, Mike, I goggled it yesterday so now I know what you are talking about.And yes, I was thinking about such solution, exactly. I guess I would need one of these units per every room, so it would be 6 of them. From what I saw on internet, one of the external units can support up to 4 internal units, that means I would need 2 systems. But do I really need 1 internal unit per 1 room?
I can't relocate the furnace, dont' have any other place for it unless I carved out space for a closet in my old living room, which I don't think my wife would go for.
And it wouldn't buy me more space because the only way I can run the big duct is right where it is running right now. There is not enough clearance elswere because the ground is sloping toward farther part of the house and at the end there is almost no clearance at all except between the rafters. Even without the ductwork it was difficult to access most of the crawl space,so you can imagine how difficult it is right now. When one of the soft ducts was demaged by a ferral cat living under our house, who made herself cozy place to sleep at, it was a nightmare to get there to fix it. The main duct, that is blocking access to most of the crawl space is huge in diameter and is meatal wraped in fiber glass insulation that is now gone from most of it. You can imagine the loss of heat through it.
I guess one suggestion would be to re-wrap the duct, but just thinking about doing it in this inhospitable place
and soon finding out that something is ripping it off again, makes me not want to do it, definitely. Besides, as I said earlier, I would like to regain the little access that I had before, so getting rid of all the ductwork is such an appealing idea to me.
I gess, I would like to know, assuming I can afford doing it, if cost of runing the 2 minisplit units in this house would be less, the same or more than running the furnace. By the way, I live in North West, Seattle area. Maybe a few days in winter time that the temps go below freezing and not much below that: 1 or 2 Deg?
Anyway, thank you very much Mike for the suggestions.
I also wander if there are other alternatives, like electric heaters? Is electric heating still prohibitively more expensive than gas these days? It use to be years ago but now I don't know. The zoning could be done easy with electric.
Maybe solar? Probably not in my neck of the woods.

"and a unit which is mounted on the wall inside the house."

Ceiling and floor mounts and small air handlers are also available, but less common and less efficient. Do you need one vor every room? Maybe not. Some people use powered jump ducts in the stud spaces. Then there are the small air handlers that I mentioned. I've posted a lot about my experience with installing and using 7 indoor units (3 outdoor) in my house. I like them and they are inexpensive to run. Gas prices have gone down considerably in the two years since mine were installed, however. See if you can find them with a search ("mini split", "mini split").

That would be "See if you can find my posts with a search".

Wow!Just finished sketching the layout in Words but then had to convert it into jpeg file! It doesn't look too good here, but I hope will be enough.
First I'll try to respond to energy_rater_la:the furnace is already in a closet, however I am not sure at this point about routing the ductwork inside. That would definitely be a huge challenge for me. Whole downstairs: 2 living rooms, nook and kitchen is open. What is approximate cost of leak test? My crawl space is enclosed, vented. I didn't contact any pros yet, since this early in the process of doing some research. I don't want to waste their time on giving me estimates if I have no idea what I want to do, yet. Yeah, keeping the gas furnace would be great, but as I said I need access to my crawl space!
ionized: I'll try to find your postings.
Thank you guys very much.

Sorry for taking so much space but I wanted improve on the house layout drawing, because it was hard to read. So there it is, hopefuly easier to read.

nice! I'd have gotten out the grid paper
pencil and ruler. never got the hang of
the cad programs.

yeah...it be tough to put ducts in fur downs.
don't think it would serve the downstairs
bedrooms very well, and upstairs would
be difficult. oh well...
all the supplies are in the floors?

costs of blower door & duct testing..as
we are all independent prices vary.
you'd want someone with experience in
both existing homes & some ductwork
hvac experience.
I'd charge $400 for the testing of
both house & ductwork.
just to give you a ballpark figure.

so lets go in another direction.
do you have a vapor barrier on the ground
under the house? how much of the duct
is flex? I'd think the existing house
would be hard pipe and the addition flex..
is that right?
I always wonder why in the world flex under
a house..but I know. cost & if it is what
the installer uses.
would you be willing to keep ducts where
they are, fix them up and make crawlspace
critter proof. this would entail sealing
venting with something like hardware cloth.

when you did the addition, from the front of the
house is the addtion under a seperate roof?

brouse up on Ionized posts. he did lots of
research. going minisplit would allow you
to remove ducting completely and seal
off holes in floors.

best of luck

Hi, energy_rater_la,

I do have vapor barrier. There is a main, huge diameter (probably 20" or so) duct running along the length of the whole house (new and old),(along the poweder room, kitchen, etc) blocking the access to the part behind it, that is hard. All the side branches to vents are flex.
The new and old parts of the house are under separate roofs.
So far I was unable to find Ionized relevant posts because there is hundreds of hits when I search for Ionized. Is there a way to look only for his posts?
I have sort of seald the crawlspace with hardware cloth but in places with plastic mesh but some critters managed to find their way in. I wander if this is achivable, actually, to seal the crawl space foolproof? If I hear that it is doable than, yes I could do it. But then again, there is this problem of accessing the crawl space.
Anyway, this brain storming with you and other guys here will help me to clarify what I want and am willing to do about it. It is learning experience for me and as you I also believe in continuous education. So lets keep talking.

hardware cloth link so you know what to purchase
@ hardware store:
http://www.meshphoto.com/galvanized/002X002D063.html

installing this with U-nails (used to hold electrical
wires) or heavy duty staples makes it strong enough
depending upon what gage hardware cloth you use.
go to hardware & look @ different gages.
things like cats will require a lighter
gage than things like possums & armadillos.
not sure what your critters are.

I'd say mastic seal the hard ducts, strap them
up, wrap with ductwrap. on flex one option is to
put the hardware cloth on them, after mastic
sealing them at takeoffs from plenum.
some people use chicken wire, but the openings
in the wire still allows mice to chew on duct
wrap. then strap them up.

seal openings (leaving a movable access for future)
with hardware cloth. put poison under house/ducts
for mice.

those are my thoughts this evening.
oh & I sent Ionized an email asking
him to stop by.
best of luck.

best of luck

OMG, reading this makes me so glad that I don't have ducts in my crawlspace anymore. Here are some of my previously-posted thoughts. I wish I had more time to edit it. I hope it is at least marginally understandable.
-------
A couple of things to keep in mind that are often left out by marketers and sellers. Most mini spits don't have back-up heat so you will not have any heat while they are defrosting. (I think I ran across at least one brand that does.) So far, the only time I find it annoying is in the morning when I want things to be warming up fastest. Otherwise, I don't really notice it. I know that with Mitsubishi's current residential equipment, the 1:1 systems have better low temp performance than the multi-splits. They are more efficient too. Even if they do have back-up heat, you can kill the efficiency pretty fast if you need back-up very often.

Keep in mind that there are alternatives to the wall-hung indoor units. They cost more, but there are units that can be dropped into ceilings and others that sit on the floor. There are also short, ducted units that would solve that big room problem by splitting the supply and return. Condensate needs to be dealt with using pumps. I have 7 of the old-fashioned wall units. The only place I would change in my house is the dining room. It is a small room and it is obtrusive there. I should have used a ceiling cassette in there. They do cost more and are less efficient.

What mini splits might not work well for is conditioning a bathroom. For that you might need one of the short ducted units to handle one room and a bathroom. Unfortunately, that will add a lot of cost.

Ceiling cassettes or small air handlers might have been less expensive to install than wall units despite the equipment cost in a couple of rooms. I thought of this when my system installation was well underway, unfortunately. The reason might be unique to my house. Since we were abandoning a duct that ran through a chase in the middle of the house, and the condensate lines that also ran through the chase, we could have very easily routed the refrigeration lines, drain lines and control/power cables through that chase for several rooms rather than going through walls and under the house. It would have required condensate pumps, but that is a relatively minor issue. This kind of thing is where installer experience is likely to be a factor.

Installing a mini-split through outside walls, as is it usually promoted, is pretty quick and straightforward (Read fast and cheap straight through the exterior walls.) compared to installing a new duct system in an existing house with no central AC. My install was done through interior walls running the lines/cables under the raised house and out to the side which was much more complicated.

If I were doing this over and I had a good duct system within a house envelope, I might stick with it to save money. The trouble is, what is a good duct system? More often than not, they are outside of the living space in older homes. In addition, they are considered good when they leak 5% of the air and they only get worse as they age. Even if the whole duct system is within the envelope, you will still get pressure differentials that can force air in or out of the house.

Summary of the factors that went into my decision: I had a crappy duct system. My system was in the attic with parts of the duct system in the attic and a trunk that was a furred-down space over the main hallway. That space was both in and out of the conditioned space. The worst part was one duct that started at the AH in the attic, dropped down under the house in a chase and ran for about 30 feet before it reached the first floor register in an addition with a flat roof (thus no attic). It then reduced in size and ran another 25 feet under the house. That part might have been mini-splitted even if the rest of the house retained a ducted system.

Mini split sellers market their good dehumidification heavily. The variable-speed-blowers and variable speed compressors would help with low-load situations better and single-speed equipment. I am sure that some variable-speed ducted systems can match it. In my climate, if you have a lot of air infiltration, you will have a humidity problem no matter what you install. No matter how good at dehumidification any cooling system is, in my climate (US, Gulf of Mexico coast) a dehumidifier is a very nice thing to have for a few weeks out of every year.

If you go mini splits, don't mount a wall unit above where you will have a bed. I saw advertising that showed that and planned that. I changed my mind figuring that at low speed, at night the cold air would sort of cascade down over the heads and be uncomfortable. I am glad that I changed my mind about it. I don't know if that cooling-mode problem would occur. What I did find, since we did the installation during heating season, is that the default programming of the heat pump mode makes the units good ceiling heaters. As they approach the set point the blower speed goes way down so hot air gets stratified near the ceiling even though the louvers are pointed down. Setting the blower speed manually to a slightly higher speed fixed that. A ceiling paddle fan would too. Putting the indoor units above the bed would have been uncomfortable if only for that reason, hot air right in the face.

As far as efficiency goes, my worst of my three "systems" is supposed to operate at SEER 17.5, and HSPF 8.9. The 1:1 systems are rated better, some over SEER 20. Obviously, I do not have to subtract duct losses from that. I appreciate the ability to put ducts within the house envelope, but you can still get pressure differentials from room to room that push air out and suck it into the house.

My house is a 1940 raised, wood-frame house that probably could have been built in 1920 for the construction techniques. It must have been conservative builder. It is notable that the house still has all the doors and walls that it ever did. (I have none of that open floor plan nonsense. If I am going to stay married, I need to be able to get away from my wife sometimes and she needs doors to slam when she gets mad at me.) We only seriously heat or cool rooms that we will be in. We are not home much either, and we are working in the kitchen a lot when home. The life style has a lot to do with our decision. Minisplits are inherently zoned and our house lay-out is such that we can take advantage of that.

I have found the remote controls of the Mitsubishi not very flexible. You can set on and off times, but you can not really make true setbacks. You might want to check the possibility of hard-wired controls and investigate closely how the remotes work for several brands.

One thing you might want to keep in mind. As of 2011, I can say that the Mitsu (and perhaps all brand) multis are less efficient than the 1:1 units and they do not do as well as the single units with heating at low temperatures. For the former, I think it stems from the fact that the compressors only throttle back to a certain percentage of max. For example, a single unit might be rated at 9000 BTU. If you only need a little cooling, and assume that they throttle back to 10%, you can efficiently get 900 btu out of them running constantly with no on/off. If a tri unit is probably 22,000 btu and can throttle back to 2200 btu with the same assumption so your compressor will be flicking on and off more often which yields poorer humidity control and not as even cooling as you might expect from looking at data from the single units. This might affect planning an install of a system. If you are going to have one single unit in addition to several multis, you might consider putting the single where it will be operating at low load a lot, like a bedroom. I have some interesting data in some service manuals that I was able to download that shows, a little indirectly, what the lowest capacity is that they will run at.

Another nice thing about mini splits compared to central is that you can run a big part of your air conditioning with a relatively small genset when the power is off. I ran my ref and chest freezer along with two of my outdoor units after Hurricane Isaac cut my power for three days. The outdoor units were each running a 6000 BTU indoor unit. The generator makes 6500W. I did not try to turn on more indoor units.

Hi Ionized,
thank you for your post. I have a few questions for you.
You mentioned air handlers vs. wall unit. What is the difference? I am still not sure how to handle those smaller rooms such as bathrooms, walk-in closet, laundry room, etc., if I do install the mini splits. Could I possibly install some small fans in existing smaller diameter flexible ducts to push air from a room having a minisplit to another that doesn't"?
And being able to run the minisplits from a generator sounds like a nice feature to have.
Thanks again.

"You mentioned air handlers vs. wall unit. What is the difference? "

I referred to air handlers that are much smaller than typical split-system air handlers. They need duct and you must find a place to hide them. Take a look at the major manufacturers' web sites. You will see what I mean. I don't know much about them.

"Could I possibly install some small fans in existing smaller diameter flexible ducts to push air from a room having a minisplit to another that doesn't"? "

That would be called "jump ducts", except that usually pressure differentials inherent to ducted systems with single returns powers the air flow. In this case you'd have to install powered jump ducts. I am sure that they can be fashioned from OTS components, but Tjernlund has a kit.

Why do you have to worry about the walk-in closets, are they so humid that you will have mold problems? If so, I would think that you have a air leaks to the exterior. Are they completely sealed off from the main room or do they have louvered doors or a vent?

I am looking at your drawing. You might be able to install a small air handler in your master closet if you are willing to part with some head space there. With that, you might be able to condition a big chunk of the downstairs. If you are willing to fur-down for some ducts in the MBr, you might be able to hit the whole downstairs. I am not saying it should be done. It might really screw up the look of that room. OTOH, it is possible that it could be done in an architecturally-pleasing way depending on the characteristics of the room.

Something similar could be considered for the bathroom or landing ceiling to do the whole upstairs. Sometimes varying ceiling heights can be interesting, but if not done right, they can be horrid.

I hope that you can find some experienced and creative installers.

Hello ionized,
Thank you for your suggestions.And sorry for not responding earlier, it's difficult for me to keep up.
OK, so I will do some more research on internet on mini-splits and air handlers but I still wander about some kind of electrical zoned heating like maybe radiant heaters that can be really flat or something of that nature.
Any thoughts on that?
Thanks.

Although efficiency can vary, you can expect at least 3x the cost in energy for electrical resistance heating vs. heat pump. You factor in how much heat you need (climate, comfort temp and the amount you use the area) and the equipment costs and decide.

Historically, nearly anyone using resistance heat is rubbing their heads trying to figure out how to do something else. That could change if nat gas costs drop low enough and gas turbine generators go on line fast enough.