hello,
I am in the process of building an ICF home and am doing the majority of the work myself. The home will have an ICF basement (about to be poured), an ICF first story, and then a wood gable roof. I have a few questions:
1. I'm believe that an HRV is a very good idea for a tight ICF home,correct?

2. I'm about to pour the basement ICF walls which, including the joist system for the first floor, will rise about 2 feet above grade. Do I need to plan on having chases for the HRV intake and outtake in this part of the wall? In other words, will the intake and exhaust be in the rim joist area, a foot or so above grade, or will they be higher up in the structure?

3. If the ducts will in fact enter and exit in this area, how big of an opening in the walls do I need to plan for? 4"?, 6"?

4. Can the intake and exhaust be next to each other, or do they need to be separated? Can the exhaust exit underneath an openable window?

5. Am I right in assuming that with an HRV system, I won't need to plan on exhaust exits for anything else in the home (bathroom fans, clothes dryer exhaust, kitchen fan, etc.) because everything will be tied into the HRV system?

Any help is appreciated. Obviously my main concern is properly locating the chases for any ductwork in the house so that I don't have to go back and drill giant holes through concrete and rebar later

Joe

In order:

1> HRV is good for any tight home, but don't assume the ICF is truly tight- it has to be properly detailed for air sealing to hit IRC2012 levels of < 3ACH/50.  The good news its that it's less detailing than on stick-built construction, but it's by no means assured. There are numerous examples of ICF homes with air leakage > 5ACH/50

2>There are many places to locate HRV- it doesn't even have to be in the basement.

3> The vent & duct sizing depends on your ventilation requirements, which depend on the volume of your house and your cfm requirements.

4> There's both a min  max separation, but as long as they're on the same side of the house with the same wind-loading they can be pretty far apart.

5> There are strong arguments (even code requirements) for kitchen exhaust venting.  If the HRV is the sole venting for the bath it must meet minimum continuous cfm requirements to meet code.  Clothes dryers should NEVER be vented into an HRV system.

Thank you very much for the reply. A couple other things. The house will be around 3300 square feet. Do you think I can assume that the chases will not need to accomidate duct larger than 6" exiting and entering the wall? Also, is it acceptable to put intake or exhaust ports for the system under a covered (but open) porch, or under the floor of that porch?
Thanks

Unless you need ridiculously high ventilation rates, 6" would be fine in a house that size.

Under the open porch roof would fine (which is no different than being protected under eaves) so long as you understand the wintertime condensation/frost potential on the exhaust vent termination (this is highly climate dependent), but under the porch floor isn't probably going to work anywhere. If you put the intake under the porch you're potentially sucking in moldy air, and if venting humid air under the porch in winter to condense on the underside of the porch and local soil you get to create that moldy condition. It's generally better on the side of the house above any potential snow line and above any roof-edge or window trim's drip-splash level, giving wide clearance to combustion or plumbing venting or dryer vents, etc.

There are some termination kits out there where the intake and exhaust for an HRV are in one unit, using vanes or vent stubs to direct exhaust air away from the intake air, but that would still be mixing substantial outflow with the intake even under the best of circumstances. Four feet of separation may be OK, but a six-foot' minimum or (sometimes even ten) foot separation is specified by some vendors. Even twice that is still fine, as long as it's on the same side of the house so that the pressures always balance independent of wind direction. It's usually spelled out in the installation manual for any given unit- download a few to get a sense. eg:

http://www.venmar.ca/DATA/DOCUMENT/14_5_en.pdf

Depeding on your climate, you should consider running direct to outside bathroom and kitchen vents. I don't believe that the small energy economy of recup energy by the HRV VS the introduced humidity is worth it at all. My 2 cents ( from a self built large ICF home owner! ) I personally run 2 6" vents high cfm fans for the kitchen exhaust ( my wife sells prepped food ) and i am using 2 4" panasonic fans for bathrooms ( outputs should be recycled in the green house on the roof terrace if i ever get to doing it! ) But i am a fan of 30min very hot showers :p haah

As Dana says, kitchen ventilation needs to be its own. I put my HRV in the attic with ducts to the bathrooms, laundry, kitchen, and attic (I use the attic space for return air for the air handler). The unit I used, UltimateAir 200DX, has provision to connect additional switches to put the HRV into boost, or high rate, mode. I have a timer in each bathroom that does this. In my case humidity in the bathroom is not a problem as my shower is totally enclosed. My intake and exhaust are on the same wall in the gable about 14' apart.

I also connected up a thermostat in the intake air flow, and one in the hallway, such that during the summer when the outdoor air temp drops below the indoor temp the HRV goes into economy mode where the heat exchange wheel stops and the HRV does a simple air exchange. This help some, but not a great deal, in cooling the house at night.

6" is fine, in fact most of the ports on HRVs are 6". BUT, if you make long runs 8", you will get better operation. Same goes for intake and exhaust; 8" are preferable if you can swing it. I used these vent caps from Seiho and everyone thinks they are kinda cool.

http://www.seiho.com/product/index7.html

Posted By build123 on 16 Nov 2012 01:46 PM
hello,
I am in the process of building an ICF home and am doing the majority of the work myself. The home will have an ICF basement (about to be poured), an ICF first story, and then a wood gable roof. I have a few questions:
1. I'm believe that an HRV is a very good idea for a tight ICF home,correct?

2. I'm about to pour the basement ICF walls which, including the joist system for the first floor, will rise about 2 feet above grade. Do I need to plan on having chases for the HRV intake and outtake in this part of the wall? In other words, will the intake and exhaust be in the rim joist area, a foot or so above grade, or will they be higher up in the structure?

3. If the ducts will in fact enter and exit in this area, how big of an opening in the walls do I need to plan for? 4"?, 6"?

4. Can the intake and exhaust be next to each other, or do they need to be separated? Can the exhaust exit underneath an openable window?

5. Am I right in assuming that with an HRV system, I won't need to plan on exhaust exits for anything else in the home (bathroom fans, clothes dryer exhaust, kitchen fan, etc.) because everything will be tied into the HRV system?

Any help is appreciated. Obviously my main concern is properly locating the chases for any ductwork in the house so that I don't have to go back and drill giant holes through concrete and rebar later

Joe

1 - Yes, HRV or ERV are mandatory for ICF homes and per 2012 IRC. With ICF the airtight walls are pretty much bullet-proof. You can't have a leaky wall with 2 5/8" EPS x 6" concrete x 2 5/8" EPS. Where it will come to play is in the windows and doors. If those are not detailed correctly, you will have air leaks. The other problem area is where the wall meets the roof area, those can also be problem points. Stay away from single or double hung windows and sliders, they leak the most air. Casements are your best bet when it comes to air sealing.

2 & 3 - I would go with 6" vents. The exact locations will really come down to the HVAC engineering. Find someone who knows what they are doing and who has worked with ICF.

4 - NO. The intake and exhaust need to be separated by a couple of feet (I believe 6' is the standard). Putting them next to each other would only cause cross contamination. I would NOT put the exhaust under an operable window. Just not a good design.

5 - NO. You will need a seperate system for the bathroom fans, the clothes dryer requires its own dedicated exhaust (unless you go ventless European heat pump) and the kitchen SHOULD have its own system but it is not mandatory unless code calls for it.

You will want to double or triple check ALL of your wall protrusions. It costs A LOT of $$$ to core out concrete after the pour, especially with the rebar. This is not your OSB wall that you can cut a hole with a Sawzall.

Thanks all, I appreciate your help,

OK so I will have separate vents for kitchen, laundry and bathrooms. I like that idea anyway, seems less complicated

At this point I am thinking that I don't want to put chases in the part of the house I am pouring now. As I mentioned before I am about to pour the basement up to the top of where the first floor joists will be. Any 6" ports in this section will end up at most 18" above grade and could easily be covered in snow in the future (I live in Vermont). So I probably would'nt want them that close to the snow anyway and should just place them higher up in the first floor when I pour it next summer correct?

As Lbear said, I need to double and triple check this now so as not to go back and drill giant holes later, but unless anyone reccommends otherwise, I'm thinking that I don't want  to have chases for an HRV that close to the ground?

If all your walls are ICF, it doesn't hurt to place 8" intake and exhaust holes in the appropriate locations (near where the HRV will be located) now, before you pour. You can always plug them later with foam. In my opinion, vents are more appropriately located higher on walls where they can be protected by the roof overhang.

Where WILL the HRV be located?

Do you need chases for the other utilities? I wish I had designed some into my ICF home.

If you have room in your plans for vertical chases (I have a corner blocked out of our walk-in closet that provides a vertical chase from the basement to the attic), then you can possibly locate your HRV in the basement and your intake and exhaust lines to a covered soffit or porch or gable end (I have planned the intake under my 8'x40' covered front porch and exhaust in the small gable end of the porch).

Don't forget penetrations for outside electrical outlets, lights near doors, water faucets, fresh air intake for wood burning fireplace, clothes dryer vent (>4"), refrigerant and condensate lines for air conditioner/heat pump (one 4" sleeve for these), water supply line, electrical supply line, phone/cable/internet line, etc. Some of this may not apply at this point unless you have a walk-out basement like I do.

ICFHybrid- The HRV will likely be in the basement, but I really don't know yet. I agree that it seems to make sense to have the vents higher up, but I won't be pouring the next story until next year so I can put chases in then.

arkie6- thanks for the reminder, I am putting in chases for all that stuff, plus extras.

Posted By build123 on 17 Nov 2012 01:02 PM
ICFHybrid- The HRV will likely be in the basement, but I really don't know yet. I agree that it seems to make sense to have the vents higher up, but I won't be pouring the next story until next year so I can put chases in then.

arkie6- thanks for the reminder, I am putting in chases for all that stuff, plus extras.

Shouldn't the HRV/ERV be located next to the air handler?

Lbear,
Do you mean that the HRV unit should be located near the intake and exhaust? I guess I figured that I can just run ducts to wherever I want the vents to be. In any case I can put the unit on the same floor as the vents if necessary, it does'nt have to be in the basement.
Joe

Posted By Lbear on 17 Nov 2012 08:40 PM

Shouldn't the HRV/ERV be located next to the air handler?

No need for that. My HRV is in the attic and the air handler is in the crawl space. The fresh air outlet from the HRV is connected to the return air duct, which begins in the attic and extends to the air handler in the crawl space. See my next comment.

Posted By build123 on 17 Nov 2012 11:38 PM
 I guess I figured that I can just run ducts to wherever I want the vents to be. In any case I can put the unit on the same floor as the vents if necessary, it does'nt have to be in the basement.
Joe

Yes, you can do that. But, and this is a big but, you have to be careful about the lengths and diameters of the ducts. The longer the duct the larger the diameter needs to be to minimize friction losses. A good HVAC contractor can calculate those for you.

You'll have to excuse my ignorance, I'm a bit confused at this point Are the HRV and the air handler two different things? Is the air handler a separate fan that connects to the whole system? Obviously I'll be contacting an HVAC contractor when the time comes, just trying to educate myself ahead of time. Thanks. Joe

Posted By build123 on 18 Nov 2012 12:02 AM
You'll have to excuse my ignorance, I'm a bit confused at this point Are the HRV and the air handler two different things? Is the air handler a separate fan that connects to the whole system? Obviously I'll be contacting an HVAC contractor when the time comes, just trying to educate myself ahead of time. Thanks. Joe

No need for excuse. If you haven't been around commercial/industrial HVAC systems you wouldn't likely come across the term, even though every home furnace has one! The term is used to specifically refer to the fan/coil unit of a heating/air conditioning system. In a home furnace it's just called the fan or blower part of the furnace. In industrial systems the heat source, boiler, heat pump, etc., is generally not integrated into the unit that has the blower. In my Daikin system the heat pump compressor unit is, naturally, outdoors and pipes come to fan unit, which is in the crawl space. Since my system has no gas burner tied to the fan it would not be correct to call the part in the crawl space a furnace. Calling it a fan or blower would be OK but air handler is technically a bit more correct. Sounds more sophisticated also!

So yes, the air handler and HRV are two different units. The air handler handles (hence the term!) all the air that circulates through the house. The HRV is also, technically, an air handler but is not referred to as such as it only handles the small portion of air that is exhausted from and drawn in to maintain air freshness.

So if your heating system will be a gas furnace, then refer to it as a furnace. If it is a heat pump then refer to the part in the house as the fan or blower unit, or if you want to sound more technical, the air handler!

Posted By build123 on 18 Nov 2012 12:02 AM
You'll have to excuse my ignorance, I'm a bit confused at this point Are the HRV and the air handler two different things? Is the air handler a separate fan that connects to the whole system? Obviously I'll be contacting an HVAC contractor when the time comes, just trying to educate myself ahead of time. Thanks. Joe

Here is a GBA Article that is very informative about ERV/HRV systems.

This is a highly recommended European HRV system: Zehnder

Ideally a HRV/ERV should be on its own duct system. Therefore your HVAC setup will have it's own air handler to push the cooled A/C or heated air throughout your home. The air handler will only activate when your run your A/C or heat but a HRV/ERV runs 24/7, unless you choose to turn it off.

"Number One - An ERV should have its own supply and return duct system. The ERV needs to draw from areas that produce humidity and other pollutants. Bathrooms, laundry rooms, and in some cases kitchen areas would have returns to the ERV. The supply from the ERV should go to bedrooms, family rooms, etc. The ERV should cycle on its own controller and not by the furnace cycles.

Number Two - An HVAC duct system does not draw air from bathrooms, laundry rooms, and kitchens. This is good design practice. The ducting requirements and demand calls of the ERV and the furnace have absolutely nothing in common. They should not be tied together.

Unfortunately doing it right is more expensive. Many contractors and ERV manufacturers use the furnace ducting as a cost cutting measure.

I can't quantify the gain in performance when an ERV is installed properly with its own duct, but here is something to consider – the only time your present (improperly installed) ERV is effective is when the furnace blower is running.

Posted By Lbear on 18 Nov 2012 04:30 AM

Ideally a HRV/ERV should be on its own duct system. Therefore your HVAC setup will have it's own air handler to push the cooled A/C or heated air throughout your home. The air handler will only activate when your run your A/C or heat but a HRV/ERV runs 24/7, unless you choose to turn it off. 

Generally speaking that is correct. However, in my case the air handler for the heat pump runs 24/7. That's the way Daikin designed it. It also has the advantage of maintaining a very stable temperature in the house. No hot or cold drafts whatever, and no warm air/cool air temp cycles as is the case with an on/off furnace.

My ERV does not run 24/7. It's on a timer that cycles it on 20 minutes every 2 hours. It also runs when a manual timer in the bathrooms is turned on, or if the humidistat in the master bath turns it on. There's no need to run an HRV 24/7.