Ventilation retrofit in cold Winter and hot humid summer climate
I’m looking for some advice on how to handle the ventilation of my 6 year old house. It is not a high performance build however it is well sealed.
I’m in the process of finishing about 1000 Sq Ft. in the basement and I’d like to take this opportunity to improve the ventilation, comfort, and efficiency of the house. I’ve been working to better air seal the basement over the past few years and after I sealed my sump, basement floor, and added a radon system I noticed my hot water heater was backdrafting. I’ve since changed to a tankless direct vent. I also noticed that my air handler is drawing quite a bit of air through the 6″ fresh air duct. There has to be a better way than letting freezing winter air or hot/humid warm air directly into the house. I plan on running my air handler fan continuously to even out the temperatures between the two floors.
It seems like there’s no perfect solution to ventilation…
Option 1: Do nothing (exhaust only ventilation)
Option 2: Fresh Air System
– Allows too much unconditioned air into the home for me to consider this a viable option
– Don’t want to end up with positive pressure in the house
Option 3: ERV/HRV
– Which system to go with?
I live in Janesville, WI which has quite a different climate than the rest of the state(we have about 150 more Cooling Degree Days than Madison).
Winters can be brutally cold and Summers are very hot and humid. You can count on one hand the number of days you can actually have the windows open in the summer. I’d say climate is much more like 5A than 6A
Would keep out much of the summer humidity but I am afraid of too much humidity in the winter. After air sealing the basement we usually sit at around 30% to 35% RH in the winter which is too high and causes condensation.
This might dry out the house too much in winter and make it too humid in summer.
– Bath fans
Seems counter productive to continue using bath fans if I install an ERV/HRV but will there be enough ventilation? Say I go with 100CFM, at 60% capacity I could draw 20 CFM from each bath. The article on GBA about this topic cautions use of ERVs.
I think what I’d do is run the HRV/ERV exhaust from all 3 bathrooms then push the supply to the return duct of the air handler.
I’m hearing from some manufacturers that I need 240 CFM of ventilation. That seems waaay too high. I think I’d rather roll the dice with the BSC formula of .01 * total sq ft + 7.5 * (Occupants+1) which is better than what I’m getting today.
– Dryer and Range hood
Not much that can be done for these at the moment. Down the road I can go with a condensing dryer. Range hood is rarely used. Will the make-up air be pulled through the HRV/ERV?
Any advice to set me straight would be much appreciated. Thanks!!
Ranch home, single story 1850 Sq. Ft. w/ basement (back wall half exposed). 4 Bedroom, 6 occupants.
– 2-coat veneer plaster on 1/2 blue board
– Poly sheeting air barrier
– Foam sealed penetrations
– 2×4 walls
– Anderson 400 series casement windows
– R13 Fiberglass batts
– Tyvek barrier
– 1″ XPS (not taped)
– Vinyl Siding
– 6/12 pitch
– Engineered trusses
– Energy heels
– Soffit and ridge venting
– R50 loose fiberglass
– 1′ wide x 10″ tall concrete footing with form-a-drain
– 8″ wide x 9′ tall basement walls
– 1″ XPS on exterior of basement walls before backfill
– Foam sill seal
– PT rim plate
– Engineered rim joist
– Spray foam sealed rim and verified by depressurizing house with 600 CFM fan
– Poly sheeting
– 4″ concrete
– Sikaflex all expansion joints, cracks, and corners
– 200 CFM Radon fan
– Air sealed sump cover
– Forced Air single-stage direct vent furnace w/ AC
– April Air 600A Bypass Humidifier (not used)
– Tankless high efficiency water heater
– Passive fresh air duct to return trunk w/backflow damper
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