Howdo I ventilate my house without adding holes
I own a (1400 sq foot)ranch house (built 1964) in the Seattle area. We have added insulation and air sealing to our attic and floor and ductwork and had the crawl space dirt floor properly covered. We hope to insulate the walls in the future. We switched from a gas furnace to a Mitsubishi ducted ductless heat pump (what our hvac guy called it) which works great. While we were putting in the heat pump the technicians found condensation and mold in our attic and our new thermostat tells us that the relative humidity in our house is high. Our roofer repaired some flashing and diagnosed condensation from poorly balanced ventilation. He is adding extra soffit vents and upgrading our attic ridge vent.
We brought in environix to advise and deal with the mold in the attic. They will dry out, treat and paint the framing and sheathing and reseal around the bathroom fans. They advised upgrading the house ventilation and want me to replace the fan in the hall full bathroom (80 sq feet) with a Panasonic WhisperGreen Select (FV-05-11VKS2 – https://www.rewci.com/whisper-green-select-fv-05-11vks1.html) + Motion Sensor (FV- MSVK1 – https://www.rewci.com/motion-sensor-fv-msvk1-for-whisper-green-select.html) Constant CFM Setting = 50 CFM. But also advise adding a make up air port in another room to avoid backdraft from my gas appliances.
Would a Panasonic whisper comfort ERV do the job adequately with out adding airports? Would the ERV ventilate the bathroom adequately after showers? If not could I add the whisper green select to the larger main bath and add the whispercomfoet erv to the smaller (47 sqfoot) bathroom. The large 80 sq foot full bath has an outside wall where I could add an air source but my other bathroom and my laundry room are both internal to the house and lack outside walls. I don’t want to add fans or air ports to bedrooms or living space. My laundry room lacks a fan. My second smaller (47 sq ft) bath has a Home Depot quality ceiling fan.
Thank you
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Replies
What other gas appliances do you still have if got rid of the furnace? If your gas hot water heater is old enough that it can be back-drafted, it's not high efficiency and is possibly due for a replacement.
This doesn't directly answer your question, but it perhaps changes the urgency of your ventilation question.
Thanks for your quick response. I have an electric water heater, but a gas stove and oven. I also have a gas fire place insert. Also 250sq feet of my home is living space converted from an attached garage. This area is heated separately from the heat pump by a very simple in the wall natural gas heater.
Aside from the backdraft issues I want to figure out the simplest way to deal with the humidity issues inside the house.
It is unlikely that you have made your 1960's ranch "too tight" or even tight enough that you require makeup air. In my experience, the majority of houses with attic moisture problems have large, uncontrolled sources of moisture inside the house and you need to address these first. You're on your way with the attic air sealing and crawl vapor barrier, but I'd check the crawl again. What do you mean by "properly" covered? The vapor barrier should be as continuous as possible, any seams fully taped, with the membrane taped or fastened to the walls and piers with battens. As airtight as possible. Look for other moisture sources next. Your kitchen range should have exterior exhaust, not recirculation. Have someone carefully inspect your wall furnace. I have found most of them leak exhaust into the house. That's a CO/safety issue as well as a moisture issue. Is the gas fireplace insert vented or "vent-free" and how often do you use it? Do you have a lot of houseplants? A hot tub or bubble tub in the bathroom? Do bath fans vent to the exterior, and do you use them? I prefer timers on bath fans over motion sensors. Controlling moisture at its source is always best/first approach.
To answer your question more directly, an HRV will remove moisture in winter when the outdoor air is cooler than the indoor air. Even though it is damp outside, the RH goes down when the air warms up. In Seattle, the only way you will remove moisture from the air in spring and summer is to dehumidify or air condition the space. The outdoor air is just too wet. During dry(ish) fall weather, the HRV will probably work OK. An ERV never removes (much) moisture from the indoor air. It can help to keep the indoor air dryer if you've already dried it out mechanically and the outdoor air is wetter than the indoor air.
Summary: Source control first. Find and fix any big sources of indoor moisture. After that, a dehumidifier is the easiest and possibly the cheapest solution, if a bit noisy. Ventilating with more humid outdoor air is rarely the solution.
Final note: In the PNW, it can be warm and humid all the time depending on location. These conditions are often enough to grow surface mold even in well vented and otherwise perfectly built attics. In most cases, that mold doesn't actually hurt anything. Not all mold is "bad" mold. None is actually good from a building standpoint, but sometimes it's just something you live with. Borate sprays (Timbor, BoraCare) are relatively non-toxic and provide some protection. Might be the best you can do.
Thanks for your thorough answer. I have asthma which was getting worse so three years ago I had the attic and crawl space cleaned out and then along with the ducts resealed and insulated by a company recommended by a local green builder. It worked as a solution I have been off asthma medication since. I know they replaced with fully taped vapor barrier. I will examine it to see if it matches your description. (I am away from home now.) I basically trusted they did it right. I told them that keeping damp from the crawl space out of the house was a goal. The electrician who was in it recently described it as clean, intact and dry.
I live in the foothills east of Seattle, on an east facing hillside with Douglas firs making shade. I would describe my summers as dry and my winters and springs as wet and chilly, Fall can be dry till late October when it begins to rain heavily. Because I live on a steep hillside I worry about my crawl space. I am thinking about installing along my house the in ground gutters described on the green basics page to try to keep my crawl space dryer.
My bath fans and my kitchen exhaust fan are vented through the roof. The environix people are going to reseal them.
My gas fireplace is vented through the chimney. I use it infrequently. The heater in the back room is used all winter on low. I will have it checked by the furnace company. They serviced the fireplace this fall. I have been trying to slowly reduce my natural gas use because of asthma. I hope to replace the gas space heater with an infrared panel. I need to keep the fireplace and wall heater as back up. We lose electricity for extended periods every few years during winter storms. Both gas heaters run without electricity and were great back up for us when our old gas furnace wouldn’t work without electricity.
I have indoor plants, cook a lot with soups etc. and dry clothes inside sometimes.
I could give up my plants and use the dryer more but I still have to cook. I really want to reduce the relative humidity in the house. I will upgrade the bathroom fans. Would exhaust only fans be acceptable?
Thank you for your time.
I have gutters on my roof. I just think the in ground gutter might be an added help.