Most cost-effective whole house ventilation solution for Massachusetts?
vew10
| Posted in Mechanicals on
I am building a Tier III home on Cape Ann and will be having a single minisplit heat source for my open kitchen/living/loft area with 2 bedrooms and a bathroom also downstairs (896 sf downstairs). I have read all the discussions regarding exhaust only ventilation vs HRV/ERV. There are many HRV systems out there at varing costs. I am trying to find the most decent cost effective solution to whole house ventilation. I was considering Lunos fans but have heard that white noise could be an issue. I am looking for quiet and also cost effective to run over time as well. Any comments would be appreciated. –
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Replies
Victoria,
If you are looking for an HRV that is "quiet and also cost effective to run," you should install a Zehnder HRV.
If you are looking for a ventilation system that has a low installation cost, install a Panasonic bathroom exhaust fan controlled by a timer.
Victoria,
If you are interested in delving deeper into questions surrounding the cost-effectiveness of HRVs, you might want to read this article: Are HRVs Cost-Effective?
Hi Martin,
I actually did read that article but saw that there were many differing opinions regarding this issue. I was wondering if there has been any updated information regarding this issue.Massachusettes has been quite cold and very snowy of late and our electric prices have increased greatly. I will be having a close to airtight envelope, 12 in dbl stud cellulose walls and 16 in cellulose ceiling. I am trying to weigh cost/benefit/comfort/moisture issues. Regarding the Pansonic exhause fans....what are the disadvantagees and why would one concider the more expensive alternative of the Zehnder HRV system. I have also read about Life Breath HRV's. Ted Benson has used these in his Unity Homes. There are so many products out there it is hard for a regular homeowner to wade through all the pros and cons. Any more thoughts would be greatly appreciated.
Panasonic works ok if doors are mostly open to rooms. Zehnder is great for all rooms, you get to close doors, you get more you pay more.
And remind me again, Where does the fresh air come from in tight envelope, energy efficient homes with exhaust only ventilation. Also is moisture a concern with exhaust only?
Victoria,
In a house with an exhaust-only ventilation system, makeup air enters the house through cracks and holes in the building envelope. If your exhaust fan is moving 60 cfm of air, you can be sure that 60 cfm of outdoor air is simultaneously entering the building.
For more information, see Designing a Good Ventilation System.
But with a Teir III house and a tight envelope would this be possible? I will have a dryer vent which may provide enough fresh air to enter.
The artcle mentioned above stated "Research shows, however, that in some homes — especially small homes with an open floor plan — exhaust-only ventilation systems work well. If the exhaust fan is well chosen — my own favorite is the Panasonic Whisper Green fan, which uses only 11.3 watts to move 80 cfm — exhaust-only ventilation systems have very low installation and operating costs. If you choose this type of ventilation system, it’s important to remember to undercut the bathroom door."
Is there more of a consensus since this article was written in 2013?
This is probably sacrilegious to do this as a newbie, but I'm going to disagree with Martin on makeup air for exhaust only ventilation.
I don't think, based on experience, that random house cracks and openings can provide enough makeup air for exhaust only in very tight houses. Our house just measured 0.38 ACH50 during our final Energy Star inspection. We have 80 CFM Panasonic fans in each bathroom (2): the duct runs are very short, straight, and properly installed. We installed two Panasonic fresh air inlets (rated up to 18 CFM each), to be conservative and figuring we could add more. This is ok when running one fan on the lowest setting of 30 CFM for continuous ventilation. These two inlets are not enough for the fan in the full bathroom when it's on 80 CFM, at most it's pulling just over 50 CFM. Imagine what this would be like without the two inlets.
The fans can pull 80 CFM each when a window is cracked.
The house de-pressurizes, but eventually equals out when the fan goes off or back to low, but that defeats the point of quickly/efficiently exhausting shower humidity. We are going to re-examine our ventilation after this winter, possibly adding 1-2 fresh air inlets.....or trying a Lunos or Twin Fresh through the wall HRV.
Maybe I'm off base and it does depend on the details of each house, but it seems like a really good idea to consider an appropriate amount of fresh air inlets for exhaust only ventilation for houses that are expected to be super tight (< 1 ACH50 ???).
What the heck is a tier or teir III house??
if one is to build a super super tight home one hires an expert to design and build such. These experts know that an HVAC will need proper air in and out folks.
Exhaust only Panasonics are not for super low ACH homes!
Brian,
Your house is extremely tight, with about half as much air leakage as a Passivhaus. As you know, Passivhaus buildings are almost always equipped with a balanced ventilation system (an HRV or an ERV). I agree with you and A.J.: buildings that meet the Passivhaus standard -- or are even tighter, like yours -- shouldn't be ventilated with an exhaust-only ventilation system.
That said, very few American homes are as tight as yours, and a Panasonic exhaust fan can provide adequate ventilation for many small homes with an open floor plan.
Sounds good and in hindsight for our house, an HRV probably/definitely(?) should have been in the plan.
More importantly, to help out those who are involved with their builds or DIY, at what point should exhaust only ventilation be written off? Many people, like Victoria, are probably planning/hoping for homes that may test at 1 ACH50 give or take. Should exhaust only not be considered for "pretty good house" levels of 1-2 ACH50?
If so, is exhaust only ventilation just appropriate for homes where air sealing isn't a big priority?
Not trying to be difficult, but there is a big focus in GBA articles/advice about the importance of air sealing. When we were helping with planning and building of our home, I took some comfort in the articles/advice that exhaust only can be appropriate for small/open/tight houses. Maybe it would be helpful to GBA readers and subscribers to update the "official" ventilation articles to better clarify when each system is appropriate?
Brian,
Thanks for the feedback. In light of your comments, I have edited my advice on exhaust-only ventilation systems in my article, Designing a Good Ventilation System.
I agree that we owe our readers good advice, and we don't want to mislead our readers. GBA provides advice to a wide range of readers -- everyone from homeowners living in 100-year-old leaky homes to people like you, who are building some of the tightest homes in the U.S.
Even in very tight homes like yours, it's possible to install an exhaust-only ventilation system, as long as you are willing to put up with the possible comfort issues associated with so-called "fresh air inlets."
I am very interested in any answers to the questions Brian has raised.
My budget is limited but I have chosen to spend much money on the house envelope....sub and side slab insulation, 12 inch double stud walls 16 inch ceiling, blown in dense pack insulation, triple paned windows. I am willing to spend the money on an effective HRV if that is what is needed but if an exhaust only system with fresh air inlets is a cost effective and viable alternative that would not jeopardize the indoor air and moisture quality, it is something that I want to consider. Hence my call out on this forum. My insulator did say that I would be under 1ACH50 by the way.
Victoria,
If you are aiming for less than 1 ach50, I recommend that you install an HRV.
Thanks Martin.
Much appreciated. I will go that route. Now the challenge is which HRV company.....I am checking out Zehnder but am also checking on Life Breath as well. The heat pump /hvac guy that came to my house this am has also used others so will also wait to hear from him. If anybody has specific HRV experiences/recommendations, I would look forward to hearing about them. Thanks.
Victoria-My architect recommended a Zehnder HRV for our pretty good house.
This info may be useful: Including commissioning, but not including installation or freight, it cost about $5400 for all parts for a pretty simple, one story, largely open plan house of about 1650 square feet of conditioned space. That's the contractor price, supposedly 20% off list. I attach the quote from Zehnder.
Thanks Steven. I have a quote for the same system. The base prices on this system have gone up 18% since your quote. I also was offered the contractors discount...maybe offered to all customers? In any case our quotes are not dissimilar. Do you know how much it cost to install? also do you know what kind of joist system your contractor was working with?
Victoria-Not installed yet. It should go in within a month or so. I don't have a number for installation, but mine should be pretty simple. Two people, two days maybe? I have the benefit of a utility space along the entire north side of the house, so all the ducts can go above the joists. Here's a photo. The ductwork will go behind the short studs, the supply ducts will come through the wall and the exhaust ducts will be in the ceilings. No need to cut into the framing at all. Of course everything is in conditioned space. The insulation is installed above the drywall shown in the photo.
Good luck with the installation Stephen. Thanks for the picture and explanation.
AJ: I too had to go chasing for the definition of "Tier III", which has a definition under rebate subsidy program for new housing in MA for meeting certain performance standards relative to a state defined "Reference Home":
http://www.masssave.com/residential/building-a-house-or-addition/find-incentives/incentive-details-12-homes-rebates?q=9bc5b6e2-a3d2-4ff2-8bc1-e7b4fc500f83
It's a bit arcane to be bandying that term outside of the very narrow Massachusetts-specific program, to be sure. I live in MA and I had no idea what was meant by "Tier III home" until a few minutes ago, and would have to dig even further to find the particulars on the Reference Home. I'd bet most home builders in MA wouldn't have a clue what that meant either.
I hate to beat a dead horse (die horse, die!) but the HRV over exhaust fan debate doesn't only depend on the air tightness of the house. If you live in a moderate climate there is a really good chance you will never reclaim the energy from the HRV that you invested to buy and install one. That's a fact that people don't understand even where I live.
The other factor involved is the size of the structure. There is less heat to reclaim the smaller the structure. Someone at BSC should come up with a graph or chart that correlates these two factors, seasonal climate temperature averages (not extremes!) and building size and determine where it makes sense to make do with an exhaust fan and where it makes sense to reclaim the heat via HRV. Theoretically this would also be charted with varying discrete house leakage rates at ach 50.
Eric,
Like you, I am loathe to flog dead animals, but many of your points are addressed in this GBA article: Are HRVs Cost-Effective?
My 1st floor will have an open kitchen living area, a small bath and 2 bedrooms total space 896sf
There will also be a loft accessible by a stairway in the livingroom that will be over the bath and bedrooms bringing the total sf to about 1350. This winter has been extreme, at least this month but I also want to plan for some greater potential gyrations in the future if the climate scientists are to be believed.
I have a wierd question...what if I aimed for a slightly higher but still great ACH50 number that would satisfy Tier III but would potentially allow an exhaust only ventilation system to function effectively. Similar issues of cost effectivness have been raised regarding the European Passiv Haus standards and the cost vs diminishing returns. I am hoping for Tier III because it provides a $7000 rebate but my goal has always been to build a really comfortable energy efficient home that is inexpensive to heat, cool and maintain for as affordable price (upfront as well as long term) as possible. I am almost 60yrs old with a limited budget and also don't have a lifetime to see a return on my investment that younger homeowners may realize. Sometimes better is the enemy of good enough........Any thoughts....?
John,
Am I correct in interpreting what you are saying ia that a well designed HRV is the way to go? Also how does one find out what the pros and cons are to the other HRV systems out there. Is there a website that has done a comparison for us lay people so that we may do due dilligence before taking the plundge? I know that the design and installation play a crucial role as well.
With a well designed HRV system the ventilation goes where it's intended/needed, and the air is coming in from a known path. With exhaust-only and a leakier building envelope there's no way to tell what fraction of the air is coming in via dirty paths vs. clean, and the incoming air may not be going where it's needed most. That's not to say you can't make exhaust-only work nearly as well, but it may involve creating known leak points in a very tight house. Exhaust-only can do a pretty good job of getting rid of the most egregious sources of indoor air pollution that are created inside the house though (kitchen & bath, mostly.)
Victoria,
Your peak heat load and the capacity of your single mini-split needs to factor in your decision making as well. I don't know what your design ventilation rate is, but the difference in peak ventilation heat load is going to be ~5-6x going from a high-efficiency HRV/ERV to exhaust only....back of the envelope for your location: perhaps 1,000Btu/hr with a top of the line HRV and 6,000Btu/hr with exhaust only.
There's no doubt in my mind who's selling the very best HRV's in North America at the moment (Zehnder)...and there's also no doubt whose systems are the most expensive (the same). There are a ton of other HRV and ERV options out there...all with their own pros and cons and tradeoffs. Some of them are quite good, some of them are pretty mediocre.
Marc Rosenbaum once reminded me: there's a lot more to ventilation than energy efficiency and cost-effectiveness (or something like that). Most of the available research and expert opinions point toward an independently ducted, balanced ventilation system as the best approach for effective ventilation.