Sizing guidelines on HRV's (ME)

Constantin

We have two HRV/ERVs here. They are exhausted out of the bathrooms and return to the main return on the AC system. Since we have 0.2ACH, they aren't really needed for the indoor air quality but I have the basement one run on a 20 min on/ 40 min off schedule. Besides exhausting two bathrooms, it also pulls air past the kitty litter, making it stink less.

The two air handlers also run on a 20 minutes on / 40 minutes off schedule. That prevents humidity levels from varying much (even though the house only has one humidistat controlling the humidifier) and keeps the air fresh throughout the house.

The HRV/ERVs go into high speed mode via the dry contacts on the control board whenever a occupancy sensor in a bathroom is triggered. That pretty much prevents any window fogging beyond 5 minutes after a shower. It also keeps smells out of the other spaces.

If the house does not have an AC system then I'd duct the fresh air of the HRV into the main stairwell. If this is a very cold location, consider fitting a small duct heater to preheat the air before it goes into the conditioned space.

If you look at the instructions published by NuTech/Lifebreath, they're pretty good. As always, there is the conflict between the desire by the contractor to run large diameter duct to keep things quiet and the aethetics of having to hide such a duct.

I really like my Lifebreath product, it's been quite dependable. Their tech support is also very helpful. However, for the ultimate ERV/HRV, I'd follow Jerry Scharf's lead and have a look at the <a href="http://www.ultimateair.com">Stirling product by Ultimate Air</a>.

[Deleted User]

Recommendatons anyone??

I have a customer asking me for information on HRV's. We usually defer to our sheetmetal contractor, but they won't be involved on this project.

Any information pertaining to sizing, termination locations etc are appreciated.

TIA

ME

Ron Gillen

Vanee HRV

Mark, Vanee.ca and Venmar.ca (same company)both have installation manuals on their web site that show typical installs,duct sizing, location,etc. as well as information on sizing. I imagine most manufacturer's have something similar but these are quite good.

Ron Gillen

Save you some time

I was just looking at the Vanee site and thought I might as well tell you where to find the information you're looking for. WWW.vanee.ca - Install manuals - Gold Series 1001&2001 Install Manual - page 6-7 sizing and geographical info - page 16-18 duct sizing, layout and registers. Hope this helps. I have the 1001 if you need real life experience opinions.

don_185

may I suggest

having a blower door test done first.You may be surpise that the envelope will give you enough infiltration.

[Deleted User]

Thanks everyone...

I will take it under advisement..

ME

D107

At what ACH does an HRV become unnecessary?

GMcD

Infiltration

Is fine if your local climate won't give you envelope condensation issues. Infiltration is uncontrolled, unheated, uncooled, un-filtered outdoor air coming into your home from where ever it damn well pleases. I don't think that's a very good way of providing make-up air for all your exhaust points, or humidity control, unless you live in a climate where it's between 60F and 80F year round with benign humidity. Even in a leaky house, a properly sized HRV to provide your CONTROLLED make-up air and ventilation is going to save money in the long run since that outdoor air won't be leaking through the envelope, even in a leaky older house.

don_185

With respect.

How can outdoor air not leak thru a leaky envelope without
some positive pressure to keep it out?
I thought all hrv and erv were balance flow system.

As for humidity in the winter on a leaking envelope even with control ventilation we find ourself adding humidifiers
and in some cases turning off hrv just to maintain some
kind of moisture.

Also have not seen that much saving over a leaky envelope
with a control ventlation verse ones without.

I must say Mr Mcdonnell I respect your opinion and have learn much from you on other site and this one as well.

I'm just not convince that a hrv or erv is needed in a loose
envelope.

With respect...don.

Unknown

I agree that it's probably not cost effective. That said, it may be nice anyway for other than efficiency reasons, as you do get to control your air quality.

And, you can run positive pressure with ERV/HRVs. One that I know of even comes with a switch to specifically do that, but with most, you just balance it "heavy" on the supply side.