HRV choice help
Hey guys,
I am getting slightly behind schedule on ordering an HRV for my double stud wall house here in southern New Hampshire. I am looking for help on choosing a model of HRV for my particular application (or other balanced ventilation system). I have done what seems like endless research on ventilation systems, negative pressure, positive pressure, balanced systems…as well as reading through all the ashrae 62.1 debacle and read most of what I could find from Joe Lstiburek and of course Martin’s book Musings of an Energy Nerd. Here is where I am at with my ventilation plan, and feel free to poke holes in it (pun intended) :
Balanced HRV with ducting
160 cfm range hood (makeup air from opening a kitchen window)
Panasonic whisper??? in each bathroom with possibly a powered intake makeup air fan in each bathroom as well (this may be a custom setup)
Backdraft dampers where required
House specs :
Southern NH
Double stud wall
One mini split per floor
Full electric house (grid tied solar)
Triple pane Matthews Brothers Windows
Intello plus
Serious air sealing
2 story
700 sq ft per floor (interior)
Open concept 1st floor (1 bath)
Typical 2 bedroom second floor (1 MAIN bath)
2 adults, 3 dogs
Night time open bedroom doors
Blower door specs coming soon, although Joe Lstiburek says he doesn’t like to size ventilation off of blower doors. I expect the house to be very tight though.
I know opinions and science is changing fast in this area. What is everyone’s current recommendations for ventilation? I heard something like half of ashrae 62.1…
My ventilation install budget is around $2500.
Any HRV brand/model opinions?
Where can I source the plastic ducting I see in everyone’s HRV installs and can’t seem to find?
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Replies
My name is James btw
James,
Q. "Where can I source the plastic ducting I see in everyone's HRV installs and can't seem to find?"
A. That's Zehnder ductwork. The reason you can't find it is probably because, when you call up Zehnder and tell the Zehnder representative that your budget for an installed HRV is $2,500, the Zehnder rep laughs and hangs up the phone. The installed cost for a Zehnder HRV -- with all that pretty white plastic ductwork -- is $8,000 to $10,000.
Range Hood
If your cooking habits are on the light side, consider just getting a recirculating range hood. Then you don't have to put another big hole in the house. This won't work for everyone, but we didn't even put a range hood in our house and it has worked out fine.
Ventilation Rate
Our house (2 people) is 1320 sq ft of conditioned space and we run one bath fan at 30cfm continuous. That was based off the older recommendation (7.5cfm/person and 1cfm/100 sq ft) and has worked well.
Ventilation System
Since you're planning on a HRV, you should be able to design it to take care of your continuous ventilation and bathroom exhaust needs (on the HRV boost mode), thereby dropping bath fans and associated makeup air from the plan. I don't have actual experience buying and installing a HRV, but you could look at Fantech, LifeBreath, and the Panasonic:
https://www.supplyhouse.com/Heat-Recovery-Ventilators-13180000
https://www.supplyhouse.com/LifeBreath-Heat-Recovery-Ventilators-27200000
https://www.supplyhouse.com/Panasonic-FV-10VEC1-Intelli-Balance-100-Energy-Recovery-Ventilator-Cold-Climate
James, you can buy Zehnder's flexible, white plastic "comfotube" ducting, its associated distribution manifold, and distribution ports separately from the rest of their system. They don't like to advertise that fact, but you just have to ask. There are minimum quantity requirements, though.
Most installers just use rigid metal ducting, which is more work to install but costs less in material. Efficiency of the ductwork depends on the design.
When you say your "ventilation install budget is around $2500," is that for the entire system, or are you separating equipment cost from the installation budget? Are you planning to hire someone to do everything, or will you be supplying some or all of the labor?
I'm in the exact same situation as James and looking for similar information. I'm in central NH and almost everything else is identical, Matthews bros windows, square footage, 3 bedrooms, one dog, one kid. I'm going for the pretty good house model and my contractor has built many homes and last one used the zehnder. He thinks he can install it himself. Does anyone have experience with other HRV's? I know the zehnder is the gold standard but what's the second and third best? Also, where would I look to find someone in the upper valley NH/VT to advise HVAC design ? Thanks, Mary
Great info so far!
Michael,
I should have clarified that my budget is $2500 for an HRV and the associated ducting and materials. I will be doing the install.
Bath fans, makeup air fans, range hood not included in that budget.
James
Mary, Glad to hear about another pretty good house in NH! I am in the Keene area.
Stick around. Hopefully you can get some good info from this post too.
James
Hi James-wondering how your house is coming along? I'm wondering about the Matthews bros windows, too much time to think about decisions. Did you get your windows and do you like them? How's the vinyl look? Also, did you put in your ERV? Are you happy with your choices? sorry about all the questions. We hope to order windows this week.
Thanks so much!
Mary
We typically install ducted HRVs in our NZRHs, but they were oversized for a small ranch we're planning, so we had foursevenfive.com quote a balanced through the wall system, which came in close to your budget. They should be ideal in your situation.
Hi James, I just got done building a similar home over in the Lakes Region of New Hampshire. Double stud, tripple pane windows, Siga interior membrane and heat pump conditioned. I too put a lot of thought into how I was going to supply air to the home.
One thing that I found that is rather unique to New Hampshire is that we have many days where there is high outside humidity and and yet a relatively cool outdoor temperature (in the 70s). We also seem to have near constant high humidity all summer long. Couple this condition with the fact that you are building a home that needs very little air conditioning due to air sealing and great insulation, and you have what amounts to a home that may experience higher indoor humidity due to HRV ventilating, (especially since many people in NH choose to finish their basements, which need very little cooling yet often have high humidity). Since indoor air quality control is not just about reducing or controling humidity levels, its still necessary to keep the HRV running at recommended levels all summer long. Many builders I have talked to have said that simply running the heat pump in dehuimidificaiton mode should be enough to control indoor humidity, but I have found that with my house there are often days I do not want to be introducing cool air into the home just to dehumidify it.
This brings me to my point. I would strongly recommend going with an ERV instead of an HRV. An Energy Recovery Ventilator will exchange moisture between the incoming and outgoing air streams and will hopefully reach an equilibrium that is less harsh than simply blowing in super humid air all summer long. This also comes back to why its so important that you properly size an mini split installation. An ERV will also be beneficial in the winter months where it is possibly you may find the freezing outdoor air to be too dry, causing static and dry skin.
Ultimately you may find that if you did finish your basement, you will need a portable dehumidifier running all summer long to control humidity levels in that basement. You could also consider a whole house dehumidifier such as the ultra-air dehumidifier, but it has a huge upfront cost ($1200) for one of their smallest models. They claim it has a long lifespan and is more efficient. In my own house, I went with the Panasonic Intelli-balance 100 cold climate ERV. I found the controls to be super user friendly with just the turn of a dial to choose what CFM from 50 to 100 you want for incoming and outgoing air.
So far, since turning it on, I have noticed that my indoor humidity went from 49% to 54%. Still on the higher side, but as you know, living in NH has been like living in the tropics the last few weeks. Adding fuel to this fire I just heard on NPR that NH is forecasting to become even more tropical in the years to come due to climate change. (as if we didnt already have enough cloudy days here)
I should add that I installed all of the duct-work for my ERV with no previous experience. All in it took about 30 hours of labor and $450 in material. Most experts recommend going with metal duct-work due to its low resistance, so I went that route. I had 3 supplies on the main floor and 2 in the basement with 2 returns in the center of the home. It was very frustrating work, but probably worth it as HVAC work is not cheap. I just had an HVAC contractor of mine come over after to balance the air streams.
Ditch the bathroom fans and add that savings to the HRV budget. They are not needed, and not desirable with a balanced system. I'd consider getting a recirculating hood as well. An externally vented hood is basically a 24/7 hole in the envelope than you can't really seal very effectively. If you decide to go with a vented hood, look into Zehnder HRVs. I know they have a feature that incorporates a vented hood, but I don't know much about it because it doesn't apply to my house.
Check your local building code, you may find that it dictates the amount of mechanical ventilation required, rather than using ASHRAE. Whatever value you end up with, I would oversize the unit by at least 50%. This allows you to run in boost mode during showers and cooking, and it also means the unit will run quieter at the continuous rate. Just make sure you get one that has multiple (user adjustable) speeds.
When you compare apples to apples, the Zehnder units are not that much more than others. Sure, a Panasonic Intellibalance is half the price of a Zehnder CA350, but it's also got half the capacity. And a lot fewer features. The Zehnder tubing and registers are pricey, but optional. If you search a bit, you can find similar tubing from other suppliers (I have no idea if the price is lower from them).
Before you purchase any plastic ducting, check with your building official for compliance. Some of them will fight you over it.
Our elecrician/ plumber installed our Zehnder hrv. He was impressed with how easy everything went together. Zehnder designed the system from our drawings and came out to commission the system. Personally I wouldn't skimp on ventilation on a new house.
The system has run continually for three years without any issues. Changing the filters is quick and simple. The boost feature is used when we shower or generate any kitchen odors or smoke.
Trevor,
Range hoods aren't explicitly required under our code here in BC, but the volume of exhaust ventilation from the kitchen area is, so it doesn't make much sense to install a recirculating one. Given that cooking is a major source of harmful indoor particulates, I think range hoods are still a good idea, whatever the energy penalty.
Malcolm,
In that scenario, I would run another HRV exhaust to the kitchen to obtain the required cfm (in the case of BC, it seems like it's 100 on an intermittent basis). In retrospect, maybe I should have done that in my house. As it is, we can get about 60cfm from the kitchen in boost mode. The bulk of the particulates should be handled by the hood filter. I spent many years living in houses with neither mechanical ventilation nor an externally vented range hood, so I suppose I have been lulled into a sense of complacency.
Trevor,
You are probably right. Concentrating the HRV exhaust in the kitchen and baths, avoiding a gas range, and cooking most meats on a barbecue (as many people do), vented range hoods may be unnecessary.
Thanks to everyone who posted up. I'm not sure if I'm any more certain of what my plan should be or if I am more unsure. I guess this is one of those areas that's still being explored and there's not a general consensus on anything yet. I think I am going to design my system (not sure what it's going to be right now) to be flexible so that I can accommodate changes to come in the industry, or even like someone posted above, to accommodate climate change. I think I am going to put some ducting in the walls before I close them up just because that seems like the hardest thing to mess with later. Along these same lines, I feel like the design with bath fans and a range hood leaves flexibility even if it means decommissioning them later. If anybody else reads through this thread, please post up any thoughts as I'm definitely not locked into anything and will be checking back in.
James
James,
Trevor Lambert gave excellent advice.
Many homes with an HRV use the HRV for bathroom exhaust venting, and this system works fine for most homeowners. You end up with fewer holes in your thermal envelope, lower installation costs, and lower energy bills. For more information, see this article: "Does a Home with an HRV Also Need Bath Fans?"
I would also consider Chris Roche's advice regarding HRV vs ERV. In any climate with hot humid summers and cold winters, an ERV can help reduce the impact of bringing in air who's moisture content differs greatly from that of the air inside the house. It's just icing on the cake that he is near where you are.
In the summer, hot/moist outside air brought in by an HRV can dramatically increase the latent load on air conditioning equipment and potentially lead to unhealthy levels of moisture in the home.
In the winter, dry outside air brought in can lower indoor humidity to uncomfortable levels. A good friend of mine barely runs his HRV in the winter because it dries his house to the point of excess static electricity buildup (shocks touching door knobs etc.), dry skin and nosebleeds.
Running an ERV will still introduce summer moisture and dry the house out in winter, but it will do so at a much lower rate than an HRV for a given level of airflow.
Ok guys review this new plan.... (after considering everything posted here)
Same house specs as above... (also just to remind people, this is slab on grade. No basement)
panasonic intelli-balance 100 cold weather ERV
pulling from each bathroom (2) and the kitchen
supplying each bedroom (2) and the living room
6" metal ducting
Bathroom boost switches
no separate bath fans
dryer is in the main bathroom, Joe Lstiburek says this will need an interlocked MUA fan.
Joe Lstiburek (website) says the house needs a 200 cfm or less range hood (hood wide,low and preferably with side walls) exhausted to outside with either a MUA fan interlocked and ducted to the toe kick on cabinet or a window opened at the far end of the house. (not near the fan as to not short circuit the extraction plum)
Have you considered a heat pump dryer? You'd be able to avoid the make up air concern and have one less hole in the wall. Ours works fine.
Whether you need a hood depends on how and what you cook. We installed a recirculation fan, but never use it. We rely on the hrv boost when needed. But we don't sear steaks in the kitchen or generate much smoke.
6" duct is probably bigger than you need for a system that will top out just under 100cfm.
A condensing (and heat pump, if possible) dryer would be far preferable to a conventional dryer with make up air. Far less complicated, and more efficient. Cost will probably be similar when you factor in the ducts, fans and extra labour involved with the conventional dryer.
I think relying on opening a window is a bad idea for a range hood, especially it being on the far end of the house. The probability of forgetting to do that is maybe small, but definitely non-zero. Where is that window going to be that it's not going to cause discomfort to someone in the winter? How long before you are sick and tired of walking to and from that window at the beginning and end of hood operation? If you insist on the externally vented range hood, I think the automatic interlocked system is the only practical way to go.
Have you looked at Lifebreath ERVs? I think they might be more economical for an equivalent size. I had an HRV priced out at around $600 CAD that could do 130cfm. I'm not sure what the up charge for the ERV version would be, or US prices.
Martin, is it necessary to say "the Zehnder rep laughs and hangs up the phone."
I genuinely appreciate your Yankee frugality, but to characterize me and my colleagues the way you did seems unnecessary...and unkind.
I will reply in greater detail to the original post soon.
John Rockwell
Zehnder America
John,
My attempt at a joke fell flat, evidently. I can see how my tone could be misinterpreted.
Lest GBA readers have any doubts about my opinion of Zehnder HRVs: Zehnder HRVs cost more to install than other brands of HRV, but Zehnder provides a top-quality product along with commissioning services. Most customers who can afford a Zehnder, and who have gone ahead and installed one, are very pleased with the performance of the products manufactured by Zehnder.