This is my first post and I hope I have the formate correct, I live and build in central Pennsylvania. I built a house in 2004 using what I thought were the best practices at the time to insure it was tight and very well insulated. Took great pains to properly vent all bathrooms, dryer and range. I used Tyvek house wrap and a 6 mill vapor barrier on walls and ceiling. Used a pre-fab basement wall system that creates a very dry basement. Customer works for a propane gas co. and had a high efficiency gas hot air system installed. They are having a very hard time with condensation on their windows in the winter. They are very unhappy with me because they feel the house is to tight and I should remove the plastic vapor barrier. The only thing I changed was using Crestline windows instead of Anderson. As a side note I built 6 new homes using all of the same building techniques in my area and had none of these problems. We have discussed the use of exhaust fans allot and they assure me they use them. It is just Mom, Dad and a teenage girl so not an excessive amount water usage. What should the RH be in the winter and should I just buy them a de-humidifier. Oh, Yea they do have a heat recovery system they use when the temp reaches 50 degrees. Any help would be welcome.
Is there a sump pit in the basement? If so is the sump lid well sealed? Are their ducts in the basement? Are they well sealed? Check basement RH in the winter in relation to RH in the living areas of the house, Check duct tightness. You could be pulling moisture through duct leaks into the living area.
Do they have gas appliances like a stove? for every pound of gas burned you pump a pound of water vapor into the house. It can be pretty significant if you are someone who cooks a lot. I would also check the Manual J that was done for the heating system that was installed. If the system was oversized then it will not run long enough to remove moisture from the air which is a very common problem with high efficiency houses. The sizing of the unit is critical. If it is oversized, it will turn on and off and keep the temperature where the client likes it, but not run long enough to cycle all the air in the house through the unit allowing moisture to build up.
Did you give back the moisture meter??
Green Building Advisor had a piece recently about a humidity situation where the HRV intake duct had standing water in it.
I had a situation where the intake was low enough the lawn mower filled it with clippings.
Have you considered the Panasonic Whisper Green continuous run fan? With the motion sensor control the guess work about is the homeowner using the vent fan goes away.
I second that motion - I've used Panasonic Whisper Greens on a couple occasions to solve a thorny IAQ problem at minimal operating expense.
No house needs 8 air changes per day, unless it's a very toxic environment. To meet the latest ASHRAE 62.2 ventilation standards (referenced in the IRC and state codes), a house needs in the range of 4-5 AC/day (0.16-0.24 ACH), depending on square footage and number of bedrooms).
An infiltrometer is a device used to measure the rate of water infiltration into soil or other porous media. I think you mean blower door and manometer.
Rather than "air exchanger", I think you're referring to a heat-recovery ventilator (HRV) or other balanced ventilation system. An exhaust-only (for cold climates) or supply-only (for warm, humid climates) whole house ventilation system meets code as well.
I build homes in northern New England with 8500 HDDs and winter minimum design temperatures of -10°. I agree that indoor humidity needs to be no more than 40%, but that much air exchange is not required to get there, as long as there are no uncontrolled moisture sources and spot ventilation is used in bathrooms and kitchens.
Excess ventilation comes with a significant energy cost - even meeting the ASHRAE minimum standard increases heating costs, but makes up for it in good IAQ and moisture control.
Building scientist and moisture expert John Straube, having worked for years in Canada's cold climate, says that a blower door result of between 2 and 3 ACH50 is ideal for moisture control when coupled with proper mechanical ventilation.
As for Retrotec, Infiltrometer™ is the trade name for their blower door, but the industry uses the same language everywhere.
I discovered your post while doing my own research on Crestline Windows and condensation. I live in the mountains of western NC; we have a similar climate to central PA (garden zone 6a). My home was built in 2002 with a complete Crestline door and window package. We have significant moisture -- and ice -- forming on the inside of the windows and doors in cold weather. I have one door that I had replaced with a Kolbe & Kolbe door because of leaking. We we get NO moisture or ice on this new door. So I have to say, I think the problem is the manufacturer. Our previous home in the same neighborhood had Anderson windows and we never had this problem.
I have begun monitoring my inside relative humidity closely. I have installed a de-humidifier in the crawl space and am in the process of investigating a whole-house dehumidifier. Also we have reduced utilization of our gas logs. I have been able to lower the inside humidity to 42% and this has ameliorated the moisture problem.
Good luck to you.