ERV – New York Passive House Discussion

Here is a discussion between myself and other Passive House people regarding what ventilation system to use in the New York Passive house Eco Brooklyn is building. I originally got a bid for an ERV from Barry Stephens at Zehnder, which I thought was expensive. That prompted me to ask around for other options. The discussion that followed gives good insight into what is available (not much) and how to lower costs.

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Barry Stephens

The Harlem project is very impressive, especially the use of totally re-cycled materials.

As per our review of the project, here is a quote for the three units. I have broken the quote out in to the three systems, and the total for all three comes to $14,613.60.

Thanks for working with us, and I look forward to seeing this project completed.

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Gennaro Brooks-Church

My ERV budget including labor and profit is $15,000. So a material cost for $14,600 isn’t going to work. Maybe I made a mistake or maybe the prices went up since last time.
I think the Zehnder prices are not sustainable. The Zehnder ERV is twice the cost of all the building’s heating and cooling and half the cost of the entire door and window budget. Maybe it is the Euro conversion or the over engineering of the product but the price is just not justifiable given the technology and materials involved to make an ERV. I can’t recommend your product as a green solution because it is inaccessible to most of the population.

I am going to speak with Floris this week about other ERV makers as well as looking into just buying the units from Zehnder and sourcing all the accessories elsewhere. What are your suggestions on just buying the units? Labor is much cheaper than the Zehnder accessories so maybe I can reduce costs there?

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Barry Stephens

Per our previous discussions, I understand your position on the cost of our systems. And I would like to point out a couple of important points to consider:

1) European ventilation systems represent a paradigm shift in thinking with regards to HVAC design and budgeting. By combining tight, well insulated envelopes with high performance heat recovery, you are able to significantly reduce your heating/cooling loads, and the cost for those systems. Which is the Passive House model.

I had a conversation with Katrin Klingenberg from PHIUS at the PHI conference in Dresden, Germany last year. She wanted us to bring in and distribute the Paul by Zehnder H/ERVs, which are almost twice the cost of the ComfoAir units. I told her that I didn’t think that we could sell them at the high prices we would need to charge, and she explained that by using a Paul unit and applying the numbers to the PHPP, a builder could potentially reduce the insulation of the entire envelope by two or three inches, or save significantly in aspects of the design.

2) I believe that our H/ERVs are a good value, based on efficiency, quiet operation, and quality and dependability. We also offer more functionality and controls than alternative brands. The Euro/Dollar exchange does increase the price modestly, and so we are what we are in that regard.

3) Our ducting systems are indeed over-engineered in some respects. They were designed for use in concrete, as well as wood framing, etc. We are aware of this, and we are developing alternative components that will reduce the cost of a system. In some cases these are plastic components, and in some cases we may manufacture components in the States to reduce costs. We are looking at these options now.

The fact that Habitat for Humanity is adopting PH as an alternative standard in some of their regions, and using our H/ERVs in these projects is testament to the viability of this model for affordable projects. We are working with affordable housing projects in CA and OR as well, and they understand that although our piece is more costly than traditional heat recovery systems, taken as a integral component of the whole-house-system approach, we are worth it in the end.

Additionally, our ducting systems have allowed for installation that is consistent with proper air distribution schemes in retrofits, and for installation in half the time as conventional ducting. I discussed this with Charlie, who agreed that you had tackled a most difficult first project at your home.

Lastly, you may have had the impression on the pricing based on the 22 2nd St project, on which we provided a personal project discount.

We have completed a number of projects in the NYC area, and to date the results are positive. From my discussions with the contractors that have installed these systems, we have been considered a good value. I hope that you will consider the above points as you go forward on this and other projects. I am confident that you and your clients will be well served by including Zehnder.

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Gennaro Brooks-Church

Thanks for the email. I have heard these points before. I still think
Zehnder is expensive. And my budget is fixed. So it is frustrating.
Maybe Floris and I can find a way to reduce material cost by sourcing
from other distributors and just buying the Zehnder units. Also
swtiching from ERV to HRV would save some money.

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Gennaro Brooks-Church

Hello Passive House friends, I just got the ERV quote back from Zehnder for the Harlem Passive
House I am building and the high price knocked me off my chair.
Totally not sustainable.

So…. do any of you have alternative manufacturer suggestions?

Or maybe you can suggest creative ways of just buying the Zehnder unit
and sourcing the accessories from another company?

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Dave Solaz

I just finished up a product development grant application to the CT Clean Energy Fund and I had reason to do some research on HRVs and ERVs for small buildings. I was drawn to the Venmar Constructo Series Product because it can be transformed from an Energy Recovery Ventilator (ERV) to a Heat Recovery Ventilator (HRV), simply by changing its core (either of which can be purchased separately). This gives you the ability to reject humidity in both the summer and winter months (if you have good reason to do, as I did).

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Floris Buisman

Venmar EKO has efficient fans, so does stay below the PHI recommended 0.45 W/m3/hr, but their heat recovery efficiency is just not there – HVI test show 83%, which means for modelling (as PHI testing is much stricter) we would have to deduct 12%, so 71%, which is below the 75% minimum for PH certification.

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Raymond Evangelista

Do you know what model you got a quote for? I know they have some new
models that are a little higher than the models we purchased. Was the
price higher then when you purchased your unit?

The Zehnder unit has the ability to change the core from erv to hrv too. I
was told a 2nd core would cost about $800 – $900.

When I looked into the units I did a lot of homework. I found that Zehnder
made the best product. I even visited two people that manufacture the
units in the northeast. The products had a simple design, but the
efficiency numbers were close to 60-70 efficiency. Needless to say that
falls short of our goal. One unit was a casing around the core. If the
core went bad you needed to replace the while unit.

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Gennaro Brooks-Church

I was quoted for two ComfoAir 200 ERV and one ComfoAir 350 ERV. Total $15k.
What company did you visit in the Northeast? Not that I guess it
maters if they are only 60-70% efficient.

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Raymond Evangelista

That does sound very high. I have the 350 and everything I purchased came
out to 10-11K.

I don’t remember the one company. The unit was junk and I wouldn’t wish it
on my worst enemy. The 2nd unit was made by building performance equipment
out of Hillsdale NJ. This is the unit where the core and the casing are
one. They claim to be at 85% efficiency, but that was pretty far from what
I noted when I was there. The outside temp was about 40 and the indoor
temp was 70. The air coming out of the unit was about 60. Needless to say
that isn’t 85%. The unit also needs two in line bathroom fans to move the
intake and exhaust air. Needless to say that also impacts the efficiency
of the units. That being said I think the units would be great for
non-PHPP projects. They are simple and very easy to troubleshoot being the
only moving parts are the fans. The units run about $2000 and you would
need two for your project. Unfortunately they don’t have a duct solution.
The last time I spoke to them they were seriously looking at the Zehnder
duct system.

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Floris Buisman

We could switch to an HRV and save $500. Humidity wise the house should be fine in the winter, as the apartments are small and thus the people produce sufficient humidity to keep it comfortable in the winter. In the summer not having an ERV would be a small energy penalty for the additional dehumiditication that the unit needs to do, but nothing major.

We can then use off the shelve parts for exhaust and supply boxes, grillers and diffusers. This should cost less $75 per exhaust or supply point.

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Jesse Thompson

We’ve used the Comfo 350 with sheet metal ductwork to save costs, still ends up $5 – $6k installed in the end. We’ve also built recently with the Venmar EKO (low watts, decent efficiency), but it still lists at $1,500 (less than the $2,200 for the Zehnder..) but is a lot louder than the Zehnder.

The fancy tubular ductwork and the super heavy gauge swiss register boxes add a lot of cost, a complete Zehnder system can get very expensive. A Zehnder box + standard US ductwork should only be $1,500 more max, if you compare to $600 Fantech HRVs that get installed for $4k or so.

The sad part is the Zehnder is the only unit I would really consider “high-end” that we’ve been around because the others are so loud, especially when they switch into defrost mode on high speed. This includes Venmar, Lifebreath, Fantech, etc. The average USA unit isn’t a very nice piece of equipment, sadly.

There’s a reason HRVs get disconnected so much I’ve realized, most are too noisy to live with in a small house.

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Kristen Simmons

Jesse,
Thanks for splitting that out. I’m about to get 2 Zehnder units. Nothing’s been priced yet, but I was beginning to get disturbed. I will be going for the comfotubes, as it is a retrofit, but I expect that the added equipment costs will be off-set by significantly reduced installation costs. Might just do it myself, as I’ve heard that it’s incredibly easy.

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Jesse Thompson

Honestly, it feels like back when the only way to get a fancy luxury car was to buy German, but once all the other manufacturers realized there was a market for high end product they started producing it very quickly, and now all nice cars are equally quiet and well built.

Early adopter’s peril.

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Philippe Campus

From what I just read, this may not provide much help at this point, but here is a document which reviews most (all?) the HRV/ERV units that were available in the US a little while back.

It shows 2 things: It is almost impossible to know all the ERV models which are out there, and what their rated performance is, behind the marketing hype. Mark Rosenbaum refered to this document in his mechanical systems presentation (phase II). Digging through this list, there may be a more affordable ERV which comes close enough, if there is a bit of leeway in your PHPP numbers; but nothing will compare with Zehnder, or we would know about it already.

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Lois Arena

Have you guys used the UltimateAir RecoupAerator and not liked it? Too loud? Not large enough?

It has the highest efficiency in the US that is UL approved anyway. Around $1500 for the unit. No fancy ductwork. They have someone on staff who specializes in Passive House applications.

Has anyone tried the mufflers that Katrin suggested?

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Lois Arena

Here’s a comparison of ERV’s done by UltimateAir

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Kristen Simmons

The UltimateAir is the only other unit I’ve been considering. It was used on a DER project up here. The builder (paul eldrenkamp) has been doing monitoring. I’ll ask him is he has any feedback from the occupants. I’ll also share the question with the PH-Boston group, to see if they have any end user feed back. It’s a small group, but with deep experience. It’d be interesting to compare published dBA with user experiencem

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Gennaro Brooks-Church

Philippe,
From what I can tell the best option right now is to go with the Zehnder box, maybe the cheaper HRV over the ERV if your climate isn’t too humid in the summer… and then all the rest you buy locally. For example Zehnder sells a sound muffler and you need two. Once you get all the adons for that it is almost $1000 just for the mufflers! But you can buy two HVAC duct mufflers for $100 total. I’m sure Zehnder makes a fine muffler but is it 10X finer?

Now whether I can get away with an HRV in NYC is another question. It gets oppressively humid in the summer.

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Barry Stephens

Your approach is perfectly fine, and we have had a few projects go that route. A couple of considerations:

1) If you use metal ducting, you may want to consider silencers only.

2) I would use ERVs, based on experience in NYC to date. We have one project with Jeremy Shannon at Prospect Architecture where he used HRVs, and the homeowners ended up upgrading the units to ERVs. This was due to high humidity levels starting this spring in the house in Brooklyn, which is fairly close to your house, on 3rd St. Virtually every other NYC project has used ERVs. Switching to CA 350s is totally fine, as long as you can accommodate the difference at installation.

As I said, I hope that we will have a more cost-effective solution in the near future, and that you will be able to justify using the full system. At the moment, I have what I have to work with and will do what I can to accommodate your projects.

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Jesse Thompson

From everything I’ve seen, your AC will be doing the dehumidifying work in your NYC summers, certainly not your ERV / HRV. An ERV reduces some of the incoming moisture in your ventilation air, but you’re still bringing it in to be dealt with, it’s a minor issue.

Anyone who opens their windows occasionally in the summer time will add moisture to a house that can only be dealt with with a compressor, your ERV will reduce the impact of wet ventilation air, but it can’t help with a humid house.

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Nicholas Lehto

I just installed the recouaerator in two homes and I’m been pretty happy with it. It isn’t a super high end piece (ie German quality), but if it gets the efficiency they claim and it doesn’t break, then who really cares how pretty it is? Both customers commented on how quiet the units are and wondered if they were even running. This could have a lot to do with the fact that they are installed in conditioned basements away from the bedrooms, but even when you are standing right next to the unit its not overly loud. Its definitely quieter than the Venmar eko 1.5 I installed in a home last year. The only real complaint you can have with it is that you need to make sure that the incoming air is above 18f to prevent the core from freezing. If the budget doesn’t allow for a brine heat exchanger or earth tube, then you have to go with an electrical element to pre warm the air. It only uses enough energy to bring the air up to 18f ., At 70cfm it uses 44w @ 10f, 265w @ 0f, and 487w @ -10f. We aren’t talking huge number, but every watt is a watt.

Enough with the HRV’s/ ERV’s, what we really need is this: http://www.nilan.dk/en-GB/Frontpage/Solutions/Domestic-solutions/Total-solutions/Compact-P.aspx. Its been in the University of Darmstadt’s winning solar decathlon home the last two years. I just got back from visiting family in Finland and while I was there I toured a Passive House that had this unit (try taking any house you’ve designed in PHPP and stick it in Helsinki, its VERY tough to meet the standard there) . The house was built by the owner of a company that manufactures rigid foam, so he had the means to experiment with some pretty cool stuff. I can share pics if anyone is interested.

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Gennaro Brooks-Church

Those wunder Nilans are how much? Around $18,000?
Amazing stuff.

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Floris Buisman

I have an ultimateair, it is pretty load and changing the energy exchange pies is not simple enough for a regular home-owner

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Barry Stephens

Jesse makes a valid point, and I would like to respond. I spent last week in NYC (Tuesday, including visit to your project), WV and VA visiting projects. Virtually every one of those chose ERVs. A couple of those chose HRVs originally, and swapped up to ERVs. I left with 9 ERV cores, and came back with 9 HRV cores. This is due to actual performance with units in the field.

One interesting discussion we are having right now is the effect of the combination of PH level envelopes and high performance H/ERVs on the performance of newer heat pumps. Specifically, we are looking at the possibility that heat pumps may be short cycling in cooling mode, resulting in inadequate dehumidification. There also may be a tendency to oversize the heat pumps, due to skepticism by the contractors with regards to PH loads. I spoke with Floris about this possible issue, and he was aware of the focus of the manufacturers to reach high SEER ratings, and the possibility that they are compromising on the dehumidification factor to reach high SEER numbers. Add short cycling to that, and you may find inadequate dehumidification using an HRV.

In consideration of that, it is very beneficial to use an ERV to significantly reduce the humidity of incoming air in humid climates. With 60-65% enthalpy efficiency, our ERVs will have a big impact on both humidity, and cooling efficiency during high RH periods.

To put the cost factor in perspective, you can consider this:

Price of fuel efficient cars –

Chevy Aveo – $12,000
Kia Forte – $15,000
Ford Fiesta – $13,200
Toyota Prius- $23,500
Civic Hybrid- $24,000

I guess that we are the Prius in the H/ERV market, and I am sure that we will see manufacturers follow suit in pursuing higher efficiency, quiet operation and reliability. But based on my knowledge of the engineering, manufacturing processes and economies of scale that we have, I would predict that our competitors’ pricing will have to rise to meet ours, or they will fall short of meeting the performance goals they set out to achieve.

Keep up the conversation. I appreciate the feedback, and share your thoughts with my colleagues in Europe. I think that you will see that we are listening, and we will develop products and systems to bring down the cost of systems.

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Floris Buisman

As Jesse and I mention, the benefit of the ERV is small in the summer – and the mini split has the capacity to take care of the heat/humidity (I know, it will result in a slightly higher electric bill). In the winter there is not much difference, although the ERV would allow the comfortable humidity levels to be preserved. With the small living spaces per person mean that the human activities (showering, cooking, breathing) per SF]]square foot should add enough humidity to keep the indoor RH around 30-45% (unless residents go on vacation for long periods of time and thus do not add humidity to the building).

There was an issue at a larger house in NY that had an HRV. There where 3 people living in over 2,000 SF house. Running the HRVs in the winter did eventually dry out the house. In that case an ERV is worth it. There is always an option for the owners to swap out the core to an ERV if they chose to do so at a later time.

It does save money on your construction budget, so you need to make the decision.

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Gennaro Brooks-Church

From what you all say I would conclude the following for a NY brownstone:
if the HVAC is sized correctly (which it is) then it will remove humidity in the summer
if the apartments are small (which they are) then human activity will provide humidity in the winter

The big question is how much added benefit the ERV will give compared to the extra cost if the budget is tight.
It is compelling that you just changed out 9 cores to ERV, although I don’t know the details of each home and how they compare to Harlem.

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Jesse Thompson

I would add one note, whether or not ERVs can keep humidity levels low in a building is completely dependent on occupant behavior. It a building is sealed up constantly and operates in a steady state, I would agree with below.

If, on the other hand, people use the building as is common practice in NYC in my experience (leave windows open until it becomes uncomfortable inside, then close them to try and gain comfort, but indoor air is now 80+ F w/ 80% humidity), I can’t see the ERV doing much to add comfort. It won’t make things even worse, but the scale feels off in terms of humidity management.

We do need dehumidification biased heat pumps, but I can’t imagine that’s on the radar of the manufacturers yet. Building Science pushes explicitly for stand-alone dehumidifiers in low-energy buildings (but higher energy than a PH…) even though they add heat to the building as they move out moisture.

Some of their reports:

http://www.buildingscience.com/documents/reports/rr-1008-building-america-enhanced-dehumidification
http://www.buildingscience.com/documents/reports/rr-0505-residential-dehumidification-systems-research-for-hot-humid-climates
http://www.buildingscience.com/documents/reports/rr-0215-dehumidification-systems-research-results

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Gennaro Brooks-Church

Jesse you bring up an important point: the massive importance of not having the unit running when windows are open. I turn off my unit when windows are open, which has been part of almost every day since this winter. but I am a contractor.
So far the conversation haso been constantly running units….aren’t we missing something…

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Jesse Thompson

My HRV runs when my windows are open. I still use less than 350 kWH for a family of four. That’s what efficient equipment is for…

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Gennaro Brooks-Church

350kWH is great! For an American…..:)

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Jesse Thompson

Only 240 last month, and that’s with all electric cooking and dryer…
I have clients in the 950+ range. Very common.

No cable box, no DVR, all LED and CFL. Couple computers on all the time, but low power computers. No furnace fans, boiler fans, have direct vent modern gas boiler, doesn’t use much juice. No AC.

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Gennaro Brooks-Church

After looking into it I have decided that if I buy the ComfoAir units from Zehnder and all the other items from other manufacturers that I can make it work within the budget we have. I would also like to use only the 350 over the smaller 200 which would save money. We could further cut costs by using an HRV over an ERV, given we will have small apartments that provide user generated humidity in the winter and will have correctly sized mini-splits in the summer that will remove humidity.

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2 comments on “ERV – New York Passive House Discussion
  1. Bill Rittelmann says:

    Great discussion! I haven’t thought about these issues for the past couple of years, but I used to do a lot of DOE Building America work when I worked for IBACOS.

    I just wanted to comment on the “muffler” or sound attenuators. I installed a RenewAire ERV in our house years ago and ended up building my own attenuator with 1″ ductboard. It was just a simple box about half the size of the ventilator with one baffle in it, but it worked great. I don’t remember if I measured the change in airflow, but it was a single-point discharge into the living room and only had 8 feet of duct. Most of the time I can’t even hear it running.

    I’m building a house now and trying to figure out where to draw the line between affordability and function.

  2. UltimateAir says:

    Thanks to all who reviewed the UltimateAir competitive analysis document.

    Apologizes for being self promotional…but one important point not mentioned here is that the RecoupAerator offers the lowest electrical footprint and highest amount of heat transfer (95%) in the industry. It’s an ideal solution for passive homes and projects seeking LEED certification.

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