Does Aerobarrier/ACH50 below 3.o make sense without managed ventilation?
I am a member of a cohousing condo project that will soon be building to 2018 code minimum in zone 4B. If the county enforces code we would at least get to an ACH5o of 3.o. The ventilation “system” is bathroom and kitchen fans.
The only energy improvement I might have an opportunity to make in my unit would be have an Aerobarrier contractor come at the appropriate stage of construction. I might be able to get permission to have passive vent with a filter installed in an exterior wall before the housewrap and stucco go on.. Getting a set of Lunos ERV units installed would be a bigger stretch at this point. A ducted HRV/ERV is almost certainly out not going to happen.
My question is, does it make any sense to try to knock down the ACH50 without managed ventilation? I will be monitoring indoor air quality, but I may end up having to turn on a bathroom fan and open a window when I need fresh air.
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At ACH 3.0, everyone ought to have an ERV, not just you. A basic ERV just brings in fresh air, it does not really help with makup air.
I'd encourage you to try for alot less than ACH 3.0. Before I built, these were just numbers, and I had no clue how incredibly more comfortable it is to live in a tight house with a properly designed and installed HVAC system. In a tight house you will want to make provisions for makeup air for kitchen exhaust; a simple damper to let in fresh filtered air will work. You can use either a balanced damper (those kind with a weight on them) or use something like the RangeRelief device.
User...022,
There a good case to be made that make-up air for a kitchen exhaust is only necessary for large CFM fans, and even then only if there are combustion appliances.
I'd note that in many (most?) multiple dwelling units, the range fans are recirculating rather than exhaust. No makeup air necessary. Of course, this is a terrible idea, with all products of combustion and cooking staying inside the space. This makes some sort of ventilation air even more important.
If the kitchen and bathroom fans both exhaust, a passive makeup air vent would help, but these only operate when the fans are running so stale air might get to be an issue at other times. They will help to bring fresh air inside when the fans are running, but unconditioned ventilation air in zone 4 will be pretty cold in winter and hot&humid in summer. A set of Lunos units would be a good minimum if possible.
They are required for exhaust fans over 400 cfm, but in reality, the makeup air must come from somewhere, and if you have a really tight house (<=1 ACH/50) you might not like the results if you don't have makeup air.
User ...022,
What are the results of not having make-up air in a house without combustion appliances?
Granted my house is only 1.4 ACH50, but I'm all-electric, I have two 400 CFM exhaust fans in the kitchen and no provision for makeup air. I've noticed no ill effects from running the fans.
"The makeup air has to come from somewhere" is exactly true. It does.
In a condo the reason for air barrier is not for leakage, the ROI will never be there on energy when you only have a couple of exterior walls to heat.
The reason you want to pay for it is for smells and noise. If this becomes an issue later, it is very expensive to fix.
I would also look at an extra layer of drywall for your main bedroom against any shared wall. If you can get in there between drywall and mudding, caulk around all drywall perimeter.
Thank you, this is a great point. Smells and noise are reason enough for me.
Could you get something like this installed as bath fans? The bath fans would be balanced and you could run them at 20cfm continuously for some fresh air.
https://iaq.na.panasonic.com/erv/whispercomfort-60
That Panasonic unit looks pretty simple, but I'd be a bit concerned that the inlet and exhaust are so close together. The fresh air may just short circuit and go right back out the exhaust. It does look like there is a sort of nozzle on the fresh air side to throw it farther from the unit, but still...
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Kyle,
I find the description and video a bit confusing. Mike Holmes seems to be conflating balanced ventilation, and make-up air. Can the unit be used to offset negative pressure caused by a fireplace as he is suggesting?
Malcom,
I hadn't even noticed the Mike Holmes video. As far as I can tell this is an ERV that needs to be balanced based on static pressure. Instead of a duct connection for fresh air supply to the house and exhaust pick up from the house there is a grill opening for each, leaving only the outdoor connections ducted.
This isn't ideal, but could replace a bathroom exhaust fan with the addition of another duct to the outdoors. At worst, this prevents a pressure imbalance from running it. At best, it provides some fresh air. As Peter pointed out, there is some concern of the fresh air being short circuited. I don't know how to evaluate this without installing one and monitoring indoor air quality.
Kyle,
"I hadn't even noticed the Mike Holmes video."
I should have known better than to watch it...
Thank you, definitely worth a look