ERV vs mold
My goal has been to make our home as efficient as possible. There are very divergent opinions out there, and many contractors speak definitively and with complete conviction (making it tough for a consumer to figure all this out). I had spray foam insulation added and was told I needed fresh air, so I got an ERV. Now - because I live in humid FL and on the water - we're having serious mold problems. - Is a dehumidifier the best option? - Do dehumidifiers use less energy than having the compressor running on our A/C (which we'd be able to do)? - Should I quit using the ERV (or do I really need the fresh air in a super tight house)? Thanks!
Well first off, congratulations on not only having a goal but also striving towards reaching it. Unfortunately, as you have found out the answers are not as always clear-cut as many would like you to believe. In many cases my answer starts off with it depends as it really does. For the easy part - all houses should have some sort of ventilation system installed. So before we get to the ERV part lets address a few easy parts... With that I am also going to assume that you probably are all electric - i.e. water heater, stove, & furnace? The first rule is you need to be able to control internal moisture gains like cooking & baths by using exhaust fans that vent directly outside. If you do not use them now, you need to start. If they do not vent directly outside, that needs to be corrected. While you are at it, check your dryer hose & line & make sure it is clean & venting outside also. As for other gains caused by you - Do you have plants inside? One or two is generally ok but anymore especially in your area definitely requires additional dehumidification or moving them outside. How active & how often are you in the house - that leads to moisture which in most areas of the country is helped by using an ERV/HRV or by opening a window / going in & out. Should you quit using the ERV - probably not as you are in an area that has some pretty high humidity rates year round. When they are low, feel free to turn it off & open a window. Might you want to stop using it 24x7 - more than likely yes. I generally size the unit using ASHRAE 62.2 (2010) but then set it up to only run every so often based on when people are home & then only for about 10 or 15 minutes in an hour. If one feels like it is stuffy, etc… the time can always be increased. As for dehumidification – unfortunately it will probably be required as your AC unit still may not be able to handle the increased moisture loads in your home even with the above fixes. With that it might only be an issue on the most humid days or where you don’t need the AC for the day For more: http://blog.sls-construction.com/2013/bs4d-ventilation-strategies