Excessive Humidity In House

velanziaNovember 13, 2009

Hey Guys:

I'm having a really really big issue with humidity. Lemme give you a small background first.

I bought this house July/2009. Brand new house. I had to keep the windows closed as there were dust outside the house because of the construction. I had a wet/damp basement as well. Not due to any outside leaks but humidity. Thats was the explanation I got from builder. I installed an A/C hoping that it would resolve but didn't had time to see it because winter months came so quickly.


Now I'm at winter months (Nov). This is where my trouble starts. In the morning upstairs windows are covered (about 4/3) with water droplets from condensation. Downstairs condensation occurs too but it covers 1/4 of each window. This is a big issue because I see 2 of my upstairs windows has mold build up.

- I always run exhaust fan when I cook

- I always run exhaust fan when I use washroom (run it for about 15-20 mins even after use).

- There are no trees in the house.

- There are four adults live in this house including me.

- Temp setting so far was 21c (day) & 17c (sleep) and now i changed everything to 25c hoping it would removed some excess humidity.

- Every morning I clean all the windows so it wont drip on to the wood trim.

Currently those are the precautions I take. Can you guys help me on this? I'm really desperate.

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It sounds like you need a whole house dehumidifier. I had a similar issue with our new house.

Our house was completed in Dec late 2007 when the air was cold and dry. I live in mid-atlantic.

As the spring thaw approached and into early summer, I noticed spots on our basement concrete floor. I thought it was mold. Turns out it was condensation which would have led to a mold problem.. At one point, our house humidity was above 70% - that's very bad.

First thing to do it buy a few termperature/humidity meters - they cost between 10 and 25 dollars. Check out amazon. Measure the humidity on each level of the house. The humidity level should be no higher than 50% in the summer and no lower than 30% in the winter. Once you know what your humidity is in the house, you can purchase DH units to fit your needs.

In the summer, you can also use your air conditioner as a de-humidifier if you have the right type of thermostat installed that allows DH operation. These tstats allow the AC to run below the set temp when the humidity in the house goes above the level that you program. I also use this approach to deal with excessive humidity when the outside temps aren't high enough for the AC to kick on.

Between the programmable tstats and the whole house DH, I solved my problem.

Check out www.iaqsource.com and review the whole house dehumidifiers section. I purchased a Sante Fe unit which was highly rated and works great.


    Bookmark   November 13, 2009 at 11:33AM
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Thanks for the info sniffdog!

I have two hygrometers. Lower level registers 60-70% and upper level registers little more than 70% while the comfort zone is 30-50%. Thanks for providing that link and I feel that those WH dehumidifiers are not in my budget.

Do you think that a standalone dehumidifier (30-35 pint) running on my upper level would work?

Please help.

Note: I live Brampton, Canada.

    Bookmark   November 13, 2009 at 4:05PM
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I was wondering if you were somewhere where it is normally very damp and probably a lot warmer than where I am, but you don't live that far from me (I'm in Hamilton) :-).

Maybe this is too simplistic, but I'm assuming you have your furnace running now as we've had a few chilly days already. If you have forced air, the usual problem would be that the air would get dry, not humid. So, do you have a humidifier that's accidentally set too high? I'm not sure of the technical term, but I have to open a vent in the furnace in the winter as it's closed when we run the air conditioner.

    Bookmark   November 13, 2009 at 8:00PM
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We have a dehumidifier in the basement and have a venmar system for the whole house. Together these work very well and keeps the humidity around 35-40% in cold weather.

    Bookmark   November 14, 2009 at 10:00AM
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I assume your lower level is the basement and upper level is second floor? Comfort zone is main floor? Those humidity levels are way too high and you need to do something. Portable DH units can work - how well will depend on the size of your house and keep in mind that you will have to empty the water collector bins frequently. You can put one in each room if you want.

If you have humidifiers on your hvac system, definately check the settings. I also have seen this issue in the winter when my main floor humidity was 45% but the second floor was above 60%. I actually had water dripping out of my second floor ceiling registers on very cold nights - thought I had a roof leak. I fixed that issue by turning back the humidifier setting to keep the main level at 40% and periodically running the second floor hvac fan to circulate air from main level to second level and back. Since nobody lives on our second level and we never run the hvac up there unless we have guests or it gets really cold, the humidified air going to our main level was rising up and getting trapped in my duct work on the second floor. When it hit the very cold inside of the ducts, it condensed and dripped out the ceiling registers.

It sounds like your house was built very tightly which is a good thing. But you may need some form of ventilation to push stale air out and bring in fresh air that is conditioned first. Did they install a Heat Recovery Vent Or Energy Recovery Vent (HRV or ERV)? If not, you might want to look into these units. They provide an energy exchange netween stale air going out and freash air coming into the house and are about 85% energy efficient. Very tight houses should have one of these - especially new houses. A lot of your building materials will outgass for a few years as they cure and you would want to get that air out and get feash air in. When you have the windows closed for a long time, do you notice any funky smells?

I just installed an ERV in my home - what a huge difference in air quality. I am kicking myself for not having done it sooner since we were breathing in polution created from inside my home.

I hope this helps.

My house was built very tight as well and we had issues with stale air in the winter or summer when we don't open windows. The ERV solved that issue.

    Bookmark   November 14, 2009 at 10:01AM
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Dehunmidifiers will help to rid the moisture. New homes will have a lot of moisture. The concrete floor in the basement could take up to 3 years to completely give up the water used in the mix. If while the house was being built and it rained before it was totally under roof, that moisture will be in the form of humidity also. Your house could shrink from 2-3 inches as it dries out.

    Bookmark   November 15, 2009 at 6:17PM
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If the humidity inside the house is consistently higher than outside, then you have a water problem . The water is coming from somewhere. You can run a dehumidifier to take the water out of the air, but in the long run, you are better off finding out how the water is getting in.

    Bookmark   November 16, 2009 at 10:41AM
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Hey Guys, thank you very much for every input!

As mentioned by the other posters, I don't have a humidifier installed in my house. I only have forced air heating system (gas) and a AC unit (which I don't use at the moment because of winter time).

I increased the heat up to 25c to be always and it actually lowered my RH to 50% lower level and 60% to upper level. (lower level is the level above the basement and upper level is the level where all the bedrooms are). Still didn't fully resolved the humidity issue. Kinda better than earlier tho.

However the new temperature setting is killing gas and my comfort level. It's too warm inside. 25c as oppose to 21c day time and 17c sleep time setting. I will be decreasing it slowly and I fear that the humidity issue will rise again.

Oh well, since I don't have enough budget for a whole house dehumidifier, I'm gonna have to stay with a mini one. Guessing 30-35 pint will work since my house is 2315sq/ft in size.

And what is a HRV/ERV by-the-way? I have few raised blocks on my roof. They look like some sort of breather holes. And definitely they are not connected to my exhaust fans, exhaust fan outlets are all on my side wall.

And input is appreciated!

    Bookmark   November 19, 2009 at 2:10PM
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Perhaps ... Rather than the ~35 pint, try the ~65 pint.
Much more efficient energy wise when set below design RH%@temp rating of something like 60%RH@80F - and much shorter noisy run time. They aren't the most quiet things.

    Bookmark   November 19, 2009 at 5:27PM
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When you raise the inside temp this allows more mositure to be absorbed by the warmer air and hence the reduced rel humidity. You would be much better off with multiple DH's to remove the moisture. With your house size, more than 1 portable unit will be needed but you can incrementally add. You need to get the humidity down to prevent any mold growth.

The Energy Recovery Vent or Heat Recovery Vent is a fan that sucks in fresh air from outside the house in exchange for stale air that is removed from inside the house. When this exchange is made, the stale and fresh air connected thermally (they are in seperate tubes that are wrapped around each other inside the machine) so that the heat from the stale air going out is used to warm the fresh cold air coming in (the opposite occurs when running the AC). A good ERV or HRV will be 85% efficient in this energy exchange. The ERV/HRV does not consume a lot of power - maybe the equivalent of a 100 to 200 watt light bulb.

Ventilation is a critical but often overlooked part of the HVAC system. If you have a tight house, you need to find a way of bringing in fresh air and exhausting stale air. The ERV/HRV helps you do that while minimizing the loss of energy expended to heat or cool the inside of your house.

if you go to the www.iaqsource.com web site, click on the Ventilation HRV/ERV tab on the left hand side of the home page. There is a nice tutorial that explains ERV/HRV operations and why they are needed. They are not cheap - i just bought the Broan whole house unit for around 900 US dollars. It has made a huge difference in the quality of the air inside my house. The heater runs more now (to make up the 15% energy loss with the ERV) but the quality of the house air is much better. It was worth the expense for me.

I am huge fan of the Holmes on Homes show and Mike Holmes is from Canada. You can go to his web site and see many episodes that deal with all aspects of HVAC. The one thing that I noticed from these shows is that the Canadian building code is much more stringent on building energy efficient houses than here in the US. The plastic wraps that are required in Canada on the inside walls of the house as a vapor barrier and air infiltration blocker is great BUT if you don't ventilate the house properly, this wrap can be problematic. That excessive mositure in your home can condense on the inside surface of the plastic (where cold air meets warm air) and can foster mold growth on the back side of the drywall. Mold loves to grow on damp paper products.

Good luck.

    Bookmark   November 20, 2009 at 10:23AM
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good info sniffdog and you're right, ventilation is critical and often overlooked. A healthy building should have a minimum of 4 complete air exchanges per day.

    Bookmark   November 20, 2009 at 7:15PM
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