Code Question ~ HRV

[DickRussell]

Joful said: ↑
I remember woodgeek setting me straight on this before, but I still honestly don't understand putting enormous effort into a house to make it as tight as a plastic baggie, and then purposefully ventilating with outside air. Seems there might be some ideal passive air exchange level, which might be less costly than the current methods of sealing tight and then venting.

yes, it is called build a normal house and let it breathe naturally.

Yes, this has been explained before. Especially for a house in a heating climate, you simply can't "build a normal house and let it breathe naturally" in any way that provides the right amount of fresh air for any particular set of conditions, let alone all conditions. That'd be a complete roll of the dice. The house will leak most in bitter cold, windy weather (US NE since yesterday noon or so), and essentially not at all when temps are 60s-70s with no wind. Just as bad, you can't control "natural leakage" at all. The amount of "natural" leakage under worst conditions may still be excessive (making the air inside bone-dry, causing cold spots - especially if heating with stove - and wasting energy) or it may be so tight that the air inside gets too humid and stuffy. Perhaps as bad is that the leakage is through the myriad cracks and holes in the shell, resulting in the insulation becoming (over time) a collecting place for tree pollen, dust, dead insect bodies, and perhaps rodent feces. Ask your wife if she really wants her "fresh air" filtered through that.

So the only practical way to build a better house, from a building science and health point of view, is what's now said: "build tight - ventilate right." Make the shell as tight as you can get it, using well-understood techniques, and provide for mechanical ventilation. In areas with a serious winter, it pays to do that through a heat exchanger (HRV, ERV), to recover much of the heat going out with the discharged air and warm up the fresh incoming air.

 

[firefighterjake]

I might have missed it Knots . . . is this a pre-fab house . . . if so, do you mind saying what company . . . and if you like it or not? Always interested in folk's opinions of pre-fab vs. conventionally built.

 

[bnther44]

Here's the house. The main floor is 1400.
View attachment 153832

The foundation has 4" of foam too. I live in a cooler.

The factory was doing a 2x10 house for someone in Canada when I was there.

That's a nice home. The two level garage system was genius!

I approached our house a little differently. I wanted to maximize airflow and natural lighting, thusly limiting the amount of electricity. Consequently, we have a cupola running the length wise - stopping at the bedrooms. The back side of the house faces West - where the wind is coming 80% of the time. The idea is to open the windows on the cupola on the east side of the house in the evening and the windows on the west side of the house at ground level - venting the summer heat out and then close things back up in the morning after the house has cooled off.

Walls are R-20, roof R-43, the basement R-12 (I think)


.

 

[Knots]

Pre-fab. Built by Epoch Homes in Concord NH.

Epoch did a good job. The site carpenter and the excavator were top notch. Electrician and plumber on site were so-so. GC was a knucklehead and the site crew didn't do a good job. Concrete guy did nice work but didn't follow the blueprint.

If I had it to do again - I would stick build with the site carpenter. I could still do the icynene walls and what not.

If you want to put something up fast pre-fab is the way to go. The house and the site work are happening at the same time. On delivery day, they set the house in the morning and had it weather tight by evening.

 

[Knots]

That's a nice home. The two level garage system was genius!

I approached our house a little differently. I wanted to maximize airflow and natural lighting, thusly limiting the amount of electricity. Consequently, we have a cupola running the length wise - stopping at the bedrooms. The back side of the house faces West - where the wind is coming 80% of the time. The idea is to open the windows on the cupola on the east side of the house in the evening and the windows on the west side of the house at ground level - venting the summer heat out and then close things back up in the morning after the house has cooled off.

Walls are R-20, roof R-43, the basement R-12 (I think)


View attachment 153835 .

Nice. Needs more garage space!

 

[dznam]

Joful said: ↑
I remember woodgeek setting me straight on this before, but I still honestly don't understand putting enormous effort into a house to make it as tight as a plastic baggie, and then purposefully ventilating with outside air. Seems there might be some ideal passive air exchange level, which might be less costly than the


Yes, this has been explained before. Especially for a house in a heating climate, you simply can't "build a normal house and let it breathe naturally" in any way that provides the right amount of fresh air for any particular set of conditions, let alone all conditions. That'd be a complete roll of the dice. The house will leak most in bitter cold, windy weather (US NE since yesterday noon or so), and essentially not at all when temps are 60s-70s with no wind. Just as bad, you can't control "natural leakage" at all. The amount of "natural" leakage under worst conditions may still be excessive (making the air inside bone-dry, causing cold spots - especially if heating with stove - and wasting energy) or it may be so tight that the air inside gets too humid and stuffy. Perhaps as bad is that the leakage is through the myriad cracks and holes in the shell, resulting in the insulation becoming (over time) a collecting place for tree pollen, dust, dead insect bodies, and perhaps rodent feces. Ask your wife if she really wants her "fresh air" filtered through that.

So the only practical way to build a better house, from a building science and health point of view, is what's now said: "build tight - ventilate right." Make the shell as tight as you can get it, using well-understood techniques, and provide for mechanical ventilation. In areas with a serious winter, it pays to do that through a heat exchanger (HRV, ERV), to recover much of the heat going out with the discharged air and warm up the fresh incoming air.

Just built a very tight house and completely agree with D.R.'s explanation. Remember the endless admonitions for "air sealing first and foremost" on this site? Follow that guidance to its logical conclusion in a new building, along with quality windows, doors, etc. and you end up with a tight building that needs mechanical ventilation. Yep, another system, but the only way to actually control ventilation in a house and do it efficiently through the "intercooler" which recycles about 80% of the heat in the outgoing air on our unit. It also uses about 45 watts in "normal" mode and has a rheostat to control fan speed. The only "mechanical" part of this unit is a simple low-speed fan, so in the pantheon of "mechanicalness" this rates pretty low - basically the same as a bathroom vent fan. During "windows open" season, it's not necessary and we shut it down. If the unit needs replacing at some point, it's an easy, 1/2 hour job and the unit is about $1,500 bucks, a replacement fan a small fraction of that.

This "tightness" and attention paid to insulation and windows will allow us to heat this 1500 sq ft place in a cold and windy location with 1 1/2 cords of wood for the entire (endless!) heating season. 40 mph constant winds for the last 24 hours with temps right around zero and no noticeable air infiltration, no drafts - wouldn't have done it any other way. Makes for a very comfortable and efficient house. JMO, but I can't see much rationale for doing it any other way.

 

[bnther44]

Just built a very tight house and completely agree with D.R.'s explanation. Remember the endless admonitions for "air sealing first and foremost" on this site? Follow that guidance to its logical conclusion in a new building, along with quality windows, doors, etc. and you end up with a tight building that needs mechanical ventilation. Yep, another system, but the only way to actually control ventilation in a house and do it efficiently through the "intercooler" which recycles about 80% of the heat in the outgoing air on our unit. It also uses about 45 watts in "normal" mode and has a rheostat to control fan speed. The only "mechanical" part of this unit is a simple low-speed fan, so in the pantheon of "mechanicalness" this rates pretty low - basically the same as a bathroom vent fan. During "windows open" season, it's not necessary and we shut it down. If the unit needs replacing at some point, it's an easy, 1/2 hour job and the unit is about $1,500 bucks, a replacement fan a small fraction of that.

This "tightness" and attention paid to insulation and windows will allow us to heat this 1500 sq ft place in a cold and windy location with 1 1/2 cords of wood for the entire (endless!) heating season. 40 mph constant for the last 24 hours with temps right around zero and no noticeable air infiltration - wouldn't have done it any other way. Makes for a very comfortable and efficient house. JMO, but I can't see much rationale for doing it any other way.

What kind of "intercooler" are you using and are you ducting it to every sleeping room?

 

[dznam]

What kind of "intercooler" are you using and are you ducting it to every sleeping room?

We're using a Venmar EKO 1.5:

(broken link removed to http://www.freshairventilation.net/sitebuildercontent/sitebuilderfiles/ekobrochure.pdf)

The "intercooler" reference refers to the heat transfer plumbing which operates similarly in principle to an intercooler on a turbocharged car engine or an aftercooler on a boat engine. I believe it is illustrated in the referenced pdf. Europe has been using this "technology" for a long time - the U.S., as usual, is slower to come around regarding energy efficiency... don't get me started on windows!

We actually have both a cottage and a house with these units installed (both Venmar EKOs). as both were built to a very tight specification (better than 0.5 ACH)

In the cottage we ran ducting "after the fact" and were limited to running ducting in the larger common spaces in an open floor plan and in one bedroom. It works pretty well - along the lines of 80/20 (80% of the benefit for 20% of the effort). That one bedroom is noticeably more comfortable than the one without the air feed, however). We leave the door to the other bedroom open at night for that reason. Prior to installing the HRV, air quality was poor and there was excessive moisture build up. We lived in it for a couple of winter months before figuring out that the HRV was a necessity, not a "nice to have."

In the house we made plans for ducting to all bedrooms (2x6 interior walls to run the 4" ducts) in the blueprints and specs based on our experience at the cottage. We also located our air exhausts (exhausting to the outside of the house) in the bathrooms and kitchen. The bathrooms have a "boost control" which allows for a timed run of the system at high speed. It works great and allowed us to eliminate the usual bathroom exhaust fans (cfm is sufficiently high to allow this under the building code) and save some heartache in independently ducting those. Works like a charm and we're very glad we invested the time to understand the benefits of these units.

 

[bnther44]

We're using a Venmar EKO 1.5:

(broken link removed to http://www.freshairventilation.net/sitebuildercontent/sitebuilderfiles/ekobrochure.pdf)

Many thanks for the info.

Is it ducted to every room? The literature shows one line feeding fresh air, with 3 lines out (if I'm reading it right).

 

[dznam]

Many thanks for the info.

Is it ducted to every room? The literature shows one line feeding fresh air, with 3 lines out (if I'm reading it right).

Yes, see my edited reply. We did duct all of the rooms - running the ducting to each room was only a modest additional cost - 4" duct is pretty cheap - just required some planning.

 

[Knots]

Yes, see my edited reply. We did duct all of the rooms - running the ducting to each room was only a modest additional cost - 4" duct is pretty cheap - just required some planning.

dznam - you may want to consider this. Since I only have three ducts, they are larger and take up some headroom in the basement. This is the only pic I could find easily, but you can see in the background some of the ducting.

 

[dznam]

dznam - you may want to consider this. Since I only have three ducts, they are larger and take up some headroom in the basement. This is the only pic I could find easily, but you can see in the background some of the ducting.

View attachment 153879

Thanks for the pic - says 1000 words! Our basement "trunk lines" are 6" while the intake/exhaust feeder lines into each room are 4". You can also "squish" 4" vents to ovalize them to fit in smaller cavities.

 

[Buzz Saw]

I could still do the icynene walls and what not.

Is Icynene a brand name or a type of foam?

 

[dznam]

Is Icynene a brand name or a type of foam?

Brand name - they have an extensive dealers/installer network and install a variety of products including open cell and closed cell foams under the Icynene brand, but their performance is basically the same as any similar density foams - there's nothing special about them. We looked at them before finally settling on an outfit that sprays closed cell foam, the components of which were manufactured by Bayer. As far as my research could tell, there was no substantive difference in the insulating or other performance of similar-density foams (comparing closed to closed and open to open). Slightly denser equals somewhat higher r-value. Some closed cell foams use water as a blowing agent which is less toxic during application if that's a factor for you. Lots of info on the subject if you google (is that a proper verb?).

http://www.greenbuildingadvisor.com/green-basics/spray-foam-insulation-open-and-closed-cell