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did you use spray foam insulation? evr? hvr?

16 years ago

We are ready to accept a bid for Sealection 500 open-cell spray poly foam. Now doing research I find out it's necessary to install either an ERV or an HRV. I called my HVAC and it sounds like it's going to run me $2,000...which seems a smidgeon steep. A few questions:

1. What's the difference between an HRV and an ERV?

2. Is there a DIY alternative?

3. What MFG do you recomment?

4. Is it truly necessary?

Thanks, Keri

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Comments (6)

bungeeii
16 years ago
I'll tell you what I did and why. Then, others can tell you why that's not good enough.

Our home has a combination of foam, fiberglass and cellulose.
Our home simply has a fresh-air intake piped into the return air duct. (As most homes do.)
Our HVAC system has a constantly running motor at low speed to circulate the air in the house, providing even temperatures.
Our home was tested for air flow and fell right in at the desired rate.
Air is removed from the home during normal use by way of;
Kitchen fan
Bathroom fans
Clothes Dryer
Door opening/closing

What do you ~need~?
There is an amount of air that is recommended by the EPA that needs to be changed over in your home. Since you're using foam, in theory you'll have a "tighter" home than most other insulation types. But, if your home was tested, you may discover that your home still provides xxxx Cubic Feet per Minute of air change-over. If that xxxx CFM number is at or above recommended levels, then the argument that you need an HRV because you have foam is moot.
If your home tested at an uncomfortably low rate, you would need a fresh-air supply to provide adequate ventilation in your home. (We would have added another fresh-air duct to our return air.)

Because our conditioned air escapes through dryer, bathroom and kitchen vents and exterior doors, there's no way to really scavenge the heat from them, thereby making an HRV useless to us.

If you don't have much usage of these exhaust vents, or you don't have an HVAC system that circulates the air, I could definitely see where an added xRV appliance would improve the air quality and comfort in your home.
Ron Natalie
16 years ago
If air goes out, it's gotta come in. Where does the makeup air for all those exhausts come from?
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bdpeck-charlotte
16 years ago
1. What's the difference between an HRV and an ERV?

HRV - Heat Recovery Ventilator
ERV - Energy Recovery Ventilator
HRV recovers heat in cold climates, while ERV recovers heat or cool in all climates. I'm not convinced there's really a difference.

2. Is there a DIY alternative?

Yes, look on www.alpinehomeair.com for ERVs and the basic air vents mentioned on by other posters. Fairly simple install except for the backpressure testing, you can download all the instructions online.

3. What MFG do you recomment?

I don't have any recomendations, but most name brands aren't DIY supported.

4. Is it truly necessary

Regardless of the tightness of your home, an ERV and filters can greatly improve the air quality of your house. If any family member has a sensitivity to mold, fungus or dust, then an ERV and Filter could make a world of difference in their health.

Just my 2 cents.
dallasbill
16 years ago
We have exactly the same kind of situation that bungeeii. Except we are in an ICF home, which is ever more air tight than stick.

Ronnatalie: fresh-air intake piped into the return air duct, doors opening/closing in/out, air leaking in from listed exhaust ducts (no, they are not hermetically sealed when not in use), no window is 1000% sealed, no door is 1000% sealed at the threshold.

As bungeeii said: "...others can tell you why that's not good enough."
Of course, said "others" haven't lived here for 2.5 years with no smell or ill effects whatsoever, did not get that recommendation from EnergyWise Structures (who spec'ed our whole home insulation and HVAC/Man J/man D), and it's been my observation that "others" generally are saying so simply because they already paid for one, or they install them for money.
carterinms
16 years ago
Somebody recommended a "skuttle" product. I thought he said it was $10-$20, but maybe I misheard. I think the linked make-up air control is what I need. It costs around $110.

Here is a link that might be useful: Skuttle
oruboris
16 years ago
I did all foam insulation and an HRV. HRV units are basically a radiator that evens out the temperature between two bodies or air. Maybe an ERV works differently, but I doubt the difference would be profound.

I did the HRV because we occasionally have a real houseful, plus I have several dogs, and I really hate it when the house gets stuffy or damp feeling due to 'used' air.

Since the heat is hydronic radiant floor, there wasn't a simple way to introduce fresh air otherwise.

Intakes in all the baths, kitchen and laundry-- the only separate vent system will be above the range.

I can't tell you how well its going to work, we havent' moved in yet...

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