HRV Detail for HWBB Home Please

don_185

The part I like the most is keeping alittle positive pressure in the envelope.Kudos.

I like maintaining 40% all year it seem to be the magic number in my area.

It been very dry in our area as of late in with all the leaky envelopes we have here the big complaints as of late
is, the humidifider are not keeping up with demand.

I see you almost gots yours dail in.Now if you would just change those old windows.

Mark Adams

HRV Detail for HWBB Home Please

Hi Gang,

Moved into my new abode in Nov 2005. It is a 2200 SF ranch, Healthy Seal insulation, 2x6 walls, Pella Designer windows, Ultra 80 boiler, three rooms of underfloor radiant with Taco RMB-1, rest is HWBB sized for 170F. So 5 zones including the basement. Ventilation is with a Fantech fan serving 2 baths on a timer that runs for 6 one hour periods per day plus regular bath fan use, kitchen hood, etc. Makeup air is from basement with a cracked vent window.

But, I'd like use an HRV instead to save on energy and reduce window sweating when the temps are near 0F. The lowest I can get the RH using these methods is about 33% which is still bit too high. (My last house was leaky and I struggled to keep the RH up, now my house if very tight and I have the opposite issue.)

So, next year I am having AC installed. Normal sized ductwork is roughed in already. I just need the AHU, condensing unit and basement tin work. The Fantech literature shows many configurations but I'd like one that allows use of the HRV without running the AHU. Can anyone point me in the right direction?

Thanks,

Mark

Clarence, NY

don_185

33%

Thats not bad.Kind of low if you ask me.Soon you will have dry skin and the shock when you touch anything.

As far as I'm concern when it comes to these tight home.
makeup air with dehumidification is the only way to go.

Check here...www.thermastor.com.

Constantin

FWIW,

33% RH in the wintertime is pretty much dead-on. IIRC, the "ideal" winter RH is between 30-40% to minimize dust mites, nose bleeds, etc.

As for using a HRV, I say go for it if the ductwork is easily accessible and you can install the additional holes (for the outdoor air supply and exhaust) without problems. Simply replace the Fantech blower with an HRV and duct it straight to the outdoors. Have it continue to run on the same schedule and see what happens.

My bathrooms are the source for stale indoor air entering the HRV and the "supply" of outdoor air is ducted into the AC return duct. Naturally, my kitchen exhaust duct is NOT connected to the HRV and I have a seperate inlet into the AC duct system that opens every time the kitchen fan runs so that the house does not go into negative pressure.

Since I have a lot of old windows and run the HRV/TRVs on a 1/3 on/off schedule, keeping the RH up is my problem. I may turn off the HRV self-cycling feature and simply have them run whenever someone enters the bathroom.

Mark Adams

RH and Pella Stuff

Hi,

Thanks for the ideas. I should mention that Pella has an FAQ with a chart showing their recommended indoor RH vs. Outdoor Temp to limit interior window condensation. When the OD temp is Zero F, they say indoor RH should be 15% or so. Here in the Buffalo area, we get OD temps of 10-25F with RH>75% all the time. You could go crazy adding or removing interior moisture on a weekly basis.

Since I'll have an AHU and ductwork for the AC system, adding the HRV in the basement makes sense. But this will not allow me to connect the bath exhaust to the HRV. If I put the HRV in the attic space, I'll not be able to connect it to the AHU unless I build a chase by stealing some interior space. My wife would poo-poo this for sure.

Thanks,

Mark

MikeL_2

tight houses

We have a similar setup to what you propose. A Lifebreath HRV which takes air from the 2 main floor bathrooms, the kitchen and the laundry room. The HRV dumps air into the house via a supply to the air handler's intake plenum. Our house is an ICF house with Dashwood/Anderson windows and was recently tested by Natural Resources Canada as the tightest house ever built in Canada (0.39 ACH at 50 pascals).

However with the 2 of us, we struggle to keep the RH at 30% during cold spells like it is now -10C day/-18C night. And we still get a little bit of moisture on the bottom of the window panes overnight. Running the HRV to get the recommended air chaanges in the house (and the bathroom clear of steam during a shower) requires a higher CFM than that required to keep the RH at 30%. So even in an uber tight house it's hard to keep the RH where one might want it. I'll shut my HRV off for a few days and see if the RH climbs at all.

Mark Adams

Ravi, if I read this correctly,

you are saying that if you run the HRV to meet your target AC/Hr, the humidity level will be less than 30%. Is this correct?

Thanks,
Mark