We're building an AAC (autoclaved aerated concrete) house in Boulder, CO in the mountains (7500 ft). 

The house will be 1450 main floor, 1450 walk out basement.  Radiant heat both floors.

It's a house built for chemical sensitivities issues.

We don't need A/C so I figured we'd go with an HRV.  Wondering which brand is best and wouldn't have issues for someone with chemical sensitivity.  And also, how to know where to put intakes/exhausts?

Hope that you house is still in good shape after the fires in Boulder area. I am also in Colorado (high mountain valley), and selected a Venmar AVS HRV EKO 1.5 for my new house. My house has some passive solar, no A/C, a natural-gas fired hot air heating with high efficiency furnace, and 1600 sq. ft. on single story with conditioned crawl space of same size. The HRV selection was based on the high efficiency ECM (electronically commutated motors) motors, an appropriate size for my house, and good reviews for the HRV. An energy consultant used by my builder indepedently recommended the same unit that I had selected. I have not had it through a winter yet, but it seems to work as advertised as best I can tell. That is, on hot days this summer, it allowed fresh air to be brought into the house with significant cooling by the air being exhausted. (I instrumented it with 4 temperature sensors for the fresh and stale air on both sides of the heat exchanger.) Outside temperatures reached a maximum in the high 90's F, and the highest indoor temperature that I observed was 76 F, but that was capturing outside air during the always cool nights to bring the house temperature to 69 F in early morning. (The house is well insulated.)

Some reviewers of other untis complained about noise with ECM motors (the hum I believe), but I cannot hear mine while running on low in the fresh air mode. I can hear it when I put it on recirculate mode, but not the hum of the motors , rather the air flow noise just like a furnace when standing near a vent. In fact, I cannot hear mine on the high setting in the fresh air mode either.

I am not sure that there is a standard way of ducting them. In my case, the only fresh air to the house comes through the HRV. So fresh air comes from outside and then, after flowing through the heat exchanger, is ducted into exit side of furnace with ducting directed to co-flow with heated furnace air. Because my conditioned crawl space needs to be vented, I have two inlets for stale air at opposite ends of the crawl space. Passive vents connect the first floor and the crawl space so the living space is also vented. Stale air is exhausted on a different side of the house from the fresh air inlet.

I cannot address your concerns about chemical sensitivities. The ducting is standard sheet metal ducting, and the heat exchanger is a type of plastic. There are washable filters upstream of the heat exchanger for both fresh and stale air.

Lee Dodge

Thank you, Lee.  The Venmar is also the one I'm looking into.  Glad to see you like it.  My only concern was with the filter material but I'll check into that more. 

Appreciate all the detail - very helpful!

ps our house is ok - thank you for asking!

> is ducted into exit side of furnace

What effect does this have on the pressure balance of the HRV? I would expect a significant negative pressurization of the house when the furnace is running.

We just built our house this past spring.  We had an Imperial PH 1.75 HRV installed for fresh air exchange.  It is extremely quiet even when on max venting.  It is on 24/7 and is averaging $0.30 per day in electric cost.

jonr-
You asked about a negative pressure balance in the house if the HRV is ducted into the exit side of the furnace. It is likely to create a slight negative pressure balance when the furnace is running, but less than the standard ventilation system in these houses that uses a 70 cfm exhaust fan only in the crawl space. It is an interesting point, and I wll try to measure it when it cools off enough to run the furnace.

woksawi-
If you are looking for a HEPA type filter, I assume that the filters in the Venmar HRV are not. The finer the filter, the greater the pressure drop, and the more power to run the fan. My filters look like a washable, room A/C filter, although there appears to be two layers to it. Venmar might provide more details.

NHgeo1-
I run my HRV full time on low, but often at 50% duty cycle between fresh air mode and recirculate mode. In the fresh air mode, the specs claim 24 W, but I think that is for each of two fans, so 48 W total, while in the recirculate mode, I think only one fan runs. For full-time on low, I get 48 W x 24 hr x 1kW/1000 W x $0.10/W = $0.12/day, except that my 3.15 kW PV panels generate more than twice the electricity that I use, so my HRV operates for free!

Lee Dodge

What size house do you have?

My husband is now worrying that the Venmar Eko won't be big enough for our house (1450 sf on main floor, 1400 on basement floor - both living spaces)

The eco store in town recommended the Sterling.

Any feedback on either is welcome.

woksawi-

Let us assume that the we take the ventilation requirements as defined by ASHRAE 62.2, an updated residential ventilation requirement, passed in May 2003. It specifies whole-house ventilation at the rate of ([number of bedrooms + 1] times 7.5 cfm plus [0.01 cfm/ft2 of conditioned space]) cfm. Let us assume that you have a 3 bedroom house, and you have two floors of 1450 sq. ft. each. According to ASHRAE 62.2, I compute that you need a minimum ventilation of 59 cfm. First of all, do you know that your house will be so tight that you need mechanical ventilation? That 59 cfm would correspond to a blower door measurement at 50 Pa of about 1180 cfm If the blower door measured higher than that, then you don't need mechanical ventilation according to ASHRAE 62.2. Assuming that your house has less than that, and that therefore you need mechanical ventilation, and further assuming zero natural ventilation from air leakage, then you need the full 59 cfm by mechanical ventilation. The Venmar AVS HRV EKO 1.5 is rated to provide, at maximum power, 80 to 157 cfm for static pressure drops of 1.2 to 0.3 in. w.g., respectively. Thus, I would conclude that the Venmar EKO 1.5 would provide the ventilation requirement as specified by the ASHRAE 62.2 standard, even if your house had zero air leakage.

What ventilation requirement specification is your husband working with?

Thank you.  I'll post his spec when he sends it to me. 

The house will be tight -- it's built from AAC blocks and mortar, the double-pane, heat mirror, krypton windows (can go into detail later), r60 attic, metal roof, and every penetration is getting sealed.  Plus, with chemical sensitivities, the HRV is a miracle working for providing fresh air (I do much better in any new house I've been in that has an HRV or ERV). 

Does it matter that we're not using a furnace? We have radiant heat so the HRV will not be connected to a furnace.

We've gotten a few bids for the Venmar Eko and each company has a different number of inlets/outlets. How best do we determine our needs?

Our main floor has a master bedroom/bath, baby's room, and kitchen/dining/living is all one.
The basement, which will be used, has three bedrooms (only one will be used full time) and one large room/playroom.

What questions should we ask to make sure we're picking the right company/set up and equipment?

We've talked to a few HVAC companies and are getting answers all across the board unfortunately.

The issue that might impact whether we can use the Venmar Eko is that we don't have ducting so the HRV will have it's own.  The way things are, the ducting might have to take more twists and turns than would be ideal.  Also, because there are bedrooms on both floors, we might need more returns and supplies than the unit can handle - although this issue has confused me because some HVAC co's say we need a return and supply in each bedroom (is that standard?) while others say we only need one return and supply on each floor.  Quite varying opinions.  We're wishing people knew more about HRVs in our area!

All this said, this is the unit I'd really like to use after all the reviews I've read.  I just don't know how to get a straight answer.  Unfortunately we have to make the decision of whom to use/what unit before the house is completely sealed so we can't do a leakage test. 

Questions - does the ducting size/turns/length, etc affect the CFM's needed? 

What is the ideal placement for supplies and exhausts?  On the main floor, we have an open kitchen/living area, then our child's room and our bedroom.  In the downstairs, we have a family room and two more bedrooms that will eventually be used, one by guests, one by our child.

Thanks

wokisawi;

why wouldn't you address your concerns and get guidance from the manufacturers tech support?

If you download the manual for the EKO HRV from the Venmar website:
http://www.venmar.ca/AxisDocument.aspx?id=494&langue=en&download=true

several ducting methods are described on page 5. If you have concerns with allergies, I suspect that method 2.2 or 2.3, in conjunction with a high quality furnace filter would be the best way to go. In both of these configurations, the fresh air from outside is deposited in the furnace cold air return duct and is forced through the furnace before being dispersed through the house. In this way, the quality of the HRV's filter is not as important as the furnace's filter. Of course, the furnace blower fan needs to be running all the time for this to work, but I believe there are ways of wiring up the HRV to start up the furnace fan when it is running.

H.

We use ductless FiWi HRV with humidity and CO2 monitors. The motors compensate if the wind is blowing or if somebody opens a door. Here is the link http://www.viking-house.ie/fine-wire-hrv.html We have built a number of AAC block houses, we usually externally insulate them to improve the insulation to Passive House standard.

I left a message for Venmar techs every day for two weeks - no response. Not a good sign.  Anyone else have Venmar CSR issues? They don't have any reps in this area (colorado) so every HRV installer in this area has no familiarity with Venmar nor do they even want to sell it since it costs them more.  It's been frustrating because that's the one I want to use.

Thank you - although we don't have a furnace b/c we're all radiant.  The HRV has it's own ducting, not through a furnace.

How much do these units cost? Available/installers in Colorado? How can I contact you personally to discuss?