Just in the midst of building 3000 sqft icf house. The home is as air tight as it gets. 
I am just wondering, we are going with a full radiant infloor heating system for main floor and basement, for the A/C we are going with the Unico High Velocity System.
Do I still require a full HRV or ERV system on top of that? Or does the Unico system accomplish the same task as an HRV or ERV? And if I do need a mechanical ventalation system, should I be going with an HRV or ERV?
The Home is in Southern Alberta Canada. Hot Summers, Cold Winters.
Sorry if this has been covered in the forum somewhere, I searched forever but have been unable to find an aswer to this question.
Thanks in advance for your help.
Ken

Yes you would still need a full HRV system installed!

John

Your radiant floors will provide heat; your Unico system will provide cool air in hot weather, but neither will provide you with fresh air you need to breath all day, every day, all year. That is the function of the HRV. Especially so since "The home is as air tight as it gets." ERVs are suggested for hot humid climates, HRVs for cold & moderate climates, so your should lprobably use an HRV. As I understand it the issue with ERVs in your climate is the possibility of the unit frosting or freezing up, but the HRV/ERV is an area of ongoing discussion among designers of air tight houses. Talk to local HVAC contractors who will stand behind the unit, read the manufacturer's litrerature, but piut one in. Yes, you do need a ventilation system.

I had started a long dissertation on the need earlier in my first post but time is not on my side! I can’t believe either the architect, contractor(radiant floor or HVAC), builder did not suggest or explain the need ofr an HRV?

 

John

thanks for the help. I thought that was the case, but I second guessed it all when I was advised incorrectly by an inexperiences HVAC installer.

Ken
I use a Unico system in my ICF house, and have a couple suggestions.
If the 2 speed fan coil is available I would go that route. I have an earlier single speed model, but it works very well. I am sized at 2.5 ton for 2100 sq. ft. My humidity is controlled very well, avg of 45-50%, but when it gets really hot, 90+ for a few days in a row, they system runs more but lowers the humidity even more while trying to hold the temp down. I did reach 38% during one extreme hot spell; but 45-50 is a desirable range!

When they install the branches, have them use ALL sound attenuation tubing. The direction to just put a 6' piece on the end is ludicrous when you then have to pay labor to cut and piece the two different types together. I had all my clients' installs done with all sound tubing.

I don't use an hrv, as I instead use controlled exhaust fans which handles my air exchange. Depending on life-style, and number of people and how often you open and close windows and doors, an HRV may not be necessary. This is to be determined after your discussions with your installer, and also your designer, and perhaps your local inspector.

Hi Ken:
Stewart Jeanes here. My understanding is as follows:
It is code that you supply fresh air into your project. It is not code that you use an HRV. Your Unico System's duct network can be used to distribute the fresh air that code requires you bring into your home. If you think that the cost of an HRV will be recovered by the money saved recovering energy from the exhausted air then by all means install one. If not than just bring fresh air into your Unico System's return air and it will be distributed throughout your home. I will ask our distributor Ecco Supply to advise you on the volume of fresh air you require. One thing to ensure is that the fresh air is not freezing up any water coils in your system. You will find a tech note on Unico's Web Site that describes adding outside air here: http://www.unicosystem.com/Portals/0/Videos/Technote%20105%20(2009-10).pdf

Ken I'm sure you still have my number, and I'd be only too happy to render whatever assistance I can.

In the interests of full disclosure I will advise other users of this forum that my firm is the Unico Representative in Ken's area.

I must be missing something here? What is being installed, my understanding is that you have radiant floor heating and AC installed. Come winter when you hit -30 C you will have an absolute horrendous problem with condensation in the interior without fresh air being brought into the interior envelope and the stale interior air being expelled!

 An HRV would seem to be essential to me if you hope to retain any of the heated air!

 

John

> The home is as air tight as it gets

Do you have an ACH50 value? Or a target for it?

Truly air tight==active ventilation required.

Using heat recovery on the ventilation air stream will be cost-effective given your heating & cooling loads, and allow you to run higher than bare-minimum ventilation rates without a huge loss in overall thermal efficiency.

In Alberta the summertime dew points are low. Average summer dew points above 15C are the exception rather than the norm in Calgary, and probably for most of southern Alberta, which is low enough that going with ERV rather than simple HRV would be of near-zero value. Running the HRV on dehumidistat control to keep it in the 30-35% relative humidity range in winter would provide sufficient ventilation air without excessive drying. In spring/summer/fall you may have to bump the dehumidistat up to keep it from running a 100% duty cycle or use another control strategy. Summertime humidity is rarely so high in your location that a 100% duty cycle would result in higher-than-healthy indoor humidity, but it might increase the duty cycle of the air conditioning at times by introducing a bit of latent load. As long as the dew point of the outdoor air is ~15C or lower the increase in latent load will be quite modest. At dew points above 20C the increase in latent load from excess ventilation air is significant, but also quite rare in Alberta.

Hopefully they will someday reduce the ~$250/year that an HRV wastes (ERV is less) and find other solutions - dehumidification, building materials that don't off gas, air filters, carbon filters, etc. It is very possible to create indoor air that is healthier than the outdoor air.

John,
 Based on having my ERV plugged into a kilowatt Meter for a few months, I think my yearly HRV costs will be around 100$ per year based on ~ 500 kwh/year total load. I keep it set to about 0.3-0.6 ach depending on the season. Total conditioned space is around 2100 ft^2 (I am including the basement in this). This represents about 15% of my total electric bill so it is not insignificant by any measure. I am also not accounting for the costs of conditioning the air that is exchanged.
 
Your mileage may vary, but these suckers are not that bad. Any other type of filtration system still takes power, so I don’t think you will realize appreciable savings.

Cheers,
Eric Anderson

The operating cost of an ERV/HRV is not limited to the power it consumes but also to condition the fresh air as the HX is not 100% eff. I would still install one as they are the best answer to issue of indoor air quality. Cant believe hvac contractor would not have brought this up. Next question would be has he ever installed one and what is his experience and level of expertise.

ilego "I would still install one as they are the best answer to issue of indoor air quality. Cant believe hvac contractor would not have brought this up. Next question would be has he ever installed one and what is his experience and level of expertise."

I agree 100%, when I built the house I'm in now (23 years ago) the three bathrooms, laundry room and one vent in the kitchen were the air intake to the HRV. I had installed, no other fans venting interior air only the HRV does. there are timers in each bathroom and the HRV comes on when they are in use! This is not rocket science but I believe are needed to lead a healthy life style!

The new house I will be building, I'm hoping that the technology has gotten better and I can have booster fans on only for the bathroom that is in use at the time so as to remove the worst of the humid air from it and not all of the rooms!

John

johnyH, remember humidity is not the only issue with IAQ. my opinion is that it is worth the energy needed to operate an ERV/HRV to reduce the amount of off gassing, carbon dioxide,radon,mold,bacteria, etc that build up in a sealed structure... when I install a HRV they are on controllers that provide .3 air exch phr. A 2000sqft ranch w 9' ceiling and full 7'10" basement equals 223 cfm continuously. Now not every house needs continuous mechanical ventilation, but if you have a icf, sip,passive solar or other house with a tight envelope you probably do.

My HRV runs 24/7 probably 250 dys/year, we open all of the windows when we can! when it's turned on it's 20 min's on 40 off I am concerned about all of the other pollutants but the air is pulled out of the most humid area's which is where the air intake vents were placed! The 20 minute timers in the bathrooms just turn the HRV on if it happens to be off at the time of use for the bathroom!

John