Advice on HRVs

[BoilerMan]

Looking for some experience from anyone with a heat recover ventilator. I have a super-tight house (built by me 4 years ago) and have been leaving a window cracked from time to time. I watch the humidity and it can get too high if we have some people over, or my wife does any heavy cooking. I had planned on installing one when I built and will have ALL ductwork inside the building envelope.

Any thoughts on pulling fresh air from a well vented attic? I have toyed with this idea, though being that that air would be slightly warmer than outside air. However fiberglass insulation up there........could become airborne under the right conditions.

I can do a blower door to find ACH natural, but I suspect it to be very low as I was extermly meticulous in air-sealing all penitrations during the build. 3,200 square feet total heated with 2,200 living space, 100% wood heat.

TS

 

[DickRussell]

I have a very tight house, verified by blower door test. I suspect yours also is very tight, since you mention the need to ventilate when you have too many guests. A very tight house does need ventilation to keep humidity down, even in winter, as human occupancy produces more moisture than leakage will handle in such a house. I chose the Lifebreath 195ECM for its dual-core, high-efficiency operation. I run it on low 24/7, year-round. If you are concerned about drawing fresh air from the ventilated attic, then just put the intake at a convenient place from directly outside, not where any idling cars are parked, and not where snow typically drifts. I doubt that drawing attic air will give you significantly warmer air in winter, while in summer it may be a lot warmer than you'd want, working against A/C. You certainly don't want to put the outlet into the attic. I put my inlet and outlet around the corner from each other and comfortably above likely snow height, to minimize the inside runs to the unit.

 

[maple1]

We put one in when we built 18 years ago. It's a Venmar, forget the model. Had to replace the blower unit about 5-6 years ago, apparently they had a bad run of them. Started making noises - from the research I did when it happened we might be lucky it didn't go up in flames. New blower still going no issues.

I would highly recommend one in any tight house. I run ours in low two-stage mode - it's off when humidity is below setpoint, when it gets above it it kicks in on low speed. The other mode is low speed below setpoint, hi speed above. Only downpoint to that is when you get a damp day outside, it'll just keep running and raise humidity in the house. I just turn it off if a day comes along like that & humidity gets up there, seems to return to normal pretty quick when the humidity gets back down outside.

 

[BoilerMan]

They are code up in Canada eh? See lots of Venmars in Canadian-built modular houses around here.

I'm looking for the most efficient unit I can afford. Venmar and Lifebreath are both on the short list. I was thinking of not sizing it to the house, rather, the number of occupants. So many ACH seems silly, think huge house with one person, or small house with many people. I was thinking of pulling air from baths, kitchen, and boiler room. Fresh air into main hallway downstairs.

Great input, thank you both!

So many things I can spend $$$$ on, still want gutters, big-screen TV, landscaping, storage shed, tractor...............

TS

 

[maple1]

Actually I'm not sure what the code requirements are exactly, and didn't back then either. I think it was just suggested to me by somebody, and after checking them out & thinking about it just decided to just do it. I ran all the pipe for it myself when we were building, or at least most of it, & installed myself. Pull from our 3 bathrooms, one end of the kitchen, & one end of the basement, push to all other rooms & other ends of kitchen & basement. Funny this thread started, just this fall I've started running mine a bit different. Before I did it more manually, and just shut the thing off on real cold winter nights & days. Afterall, even though it transfers heat from outgoing air to incoming, it's still pretty darned chilly air you're bringing in if it's -20c out. Now, I've just let it do it's own thing for the past month at a constant humidity setting (I think around 40%), and once it gets the humidity down to that & stabilized, it really doesn't seem to cut in much at all. Sometimes I'll manually bump up to 'mode 2' - say in the evening if there's multiple showers going on upstairs leading to concentrated humidity in a couple bathroom areas up there that the control won't see for a while since it's downstairs. Then bump it back down on the way to bed.

Either way, I think they're a good investment for a tight house. Really helps with air quality, and newer ones have better filtering, I think HEPA, too. Last time I looked at one in the local building supply place earlier this year, they're still less than 1k for a higher end one. The piping to each room would be the tough part.

 

[DBoon]

For highest efficiency, buy a unit with a brushless DC (or electronically commutated) motor - it will pay for itself in electricity savings through better efficiency at lower fan speeds.

 

[byQ]

I'm building a small tight house and am going to get a HRV, too. I found this site during my research,

***Note*** this page opens to ERV ratings. To get to HRV ratings click HRV Ratings at end of 1st paragraph.
www.hvac-for-beginners.com/heat-recovery-ventilator-ratings.html

I guess the units are rated by a repairman (men?). Also includes warranties in his ratings. They rated the Nu-Air a 5* (highest rating).

 

[Floydian]

Hi Taylor,

Maybe you have read these but in case you haven't there is some really good info:

http://www.greenbuildingadvisor.com/blogs/dept/musings/how-much-fresh-air-does-your-home-need
http://www.greenbuildingadvisor.com/blogs/dept/musings/are-hrvs-cost-effective

Noah

 

[Floydian]

Hello byQ,

I'm building a small tight house and am going to get a HRV, too. I found this site during my research,

Have you checked these out? http://www.foursevenfive.com/index.php?main_page=product_info&cPath=70_71_98_99&products_id=239

Pretty slick little idea that could work really well for a small open space. Easy install and no duct work!


Noah