Ultimate Air vs. Zehnder HRV
I recall seeing in the comments for the article discussing a new way to duct hrv’s that one of the Zehnder reps was disparaging the Stirling Technologies Recoupaerator 200dx for having something to the effect of misleading, incorrect, etc. performance numbers and that it does not stack up to Zehnders products. I was wondering if that rep and anyone else could clarify why the Zehnder product would be better than the 200dx and how they differ in function? The cost of the 200dx is significantly less.
Also the last time I checked the Zehnder numbers for their HRV’s were all in Metric units. What do their units draw in Watts?
I have been recommending both companies and I was curious what the differences are besides cost?
Also the Zehnder comfotube system should be compatible with any hrv correct?
Thanks,
Spencer
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Spencer,
You can find the specifications for Zehnder HRVs on the Zehnder website. For example, here are the specifications for the ComfoAir 200.
You asked about the power consumption in watts of Zehnder HRVs. Watts are used in Europe (as in the U.S.) to measure power. You are correct that the airflow ratings of Zehner HRVs are provided in cubic meters per hour instead of cfm; however, the conversion rate is simple:
1 cubic meter per hour = 0.588 cfm
The Zehnder ComfoAir 200 draws 20 watts at 53 cfm, and 143 watts at 150 cfm.
Thanks, that is part of what I was looking for. A year or so ago all I could find was their Passivehaus cert and it didn't make much sense. It did not list the watts used on that. I think it just said it met their "standard" for efficiency but it didn't elaborate on what that was.
Does anyone know about the functional differences between the two companies systems? I saw looking through the manual that Zehnder also includes a "clima-cool" function just like the 200dx has. I am really curious why engineers and/or propagandists from either company believe their product is better than the other.
I am also still wondering about the comfotubes compatibility with other systems...it seems like it would work if you made your own manifold or modified the one they sell to fit a different unit.
Thanks,
Spencer
Hello Spencer,
There is information from third party testing on Zehnder units. We are listed with the ComfoAir 350 with both PHI and HVI. You can see the HVI listing at http://www.hvi.org. Then download the product listings in category three, which is HRVs and ERVs. You will see that the CA 350 uses about .32 watts/cfm, at 99 cfm and has Apparent Sensible Effectiveness (ASE) of 93%, and Sensible Recovery Efficiency (SRE) of 87%. The UltimateAir Recuperator is no longer listed by HVI, but when it was the Recuperator used .72 watts/cfm at 101 cfm, and ASE was 94%, and SRE was 83%.
So in a nutshell, our equivalent unit uses less than half of the electrical power, and achieves better SRE by 4%. One critical difference in the units is the cross-flow leakage, which contributes highly to an enhanced ASE percentage, as outgoing, warm air is transferred to the incoming cold air. This results in a appearance of high efficiency. The Recuperator, running at its lowest speed, has leakage above 10%. The ComfoAir 350 has leakage of 0.4%.
And finally, based both on lab results and feedback from the field, the Zehnder units are extremely quiet running, which is critical in today's highly insulated, tight homes which also have triple-glazed windows in many cases.
The full range of Zehnder H/ERVs that are sold in North America do have Passive House Institute certificates. At the bottom right of the certificates is the PHI net efficiency number, along with the electrical efficiency as measured in watts/cubic meter/hour. It is also good to understand that PHI measures the outgoing air stream, whereas the HVI protocols measure the incoming air stream. These numbers are often different, and PHI is primarily interested in how many BTUs are being expelled to the outside of the envelope, as opposed to what the temperature is coming in, which is influenced by heat from the electric fan motors/enthalpy wheel motor, cross-flow leakage, and casing heat transfer.
I hope that this helps in understanding what the numbers mean.
Barry Stephens
Business Development and Technology Director
Zehnder America, Inc
That is exactly the information I was looking for. I had done all of this research in the past before Zehner was certified by HVI and just after the Recoupearator was delisted (although I was able to find the list that still included it) and I really did not want to spend an entire day researching this stuff all over again. Really I am just scared about what my wife would say if I told her that is all I did in a days work. Anyway, the Zehnder unit is clearly then top of the heap in both quality and cost, but in your opinion where does the Recoupaerator stand? Even with trumped up numbers would it still be the #2 unit in both energy use (except maybe the 13watt Venmar) and recovery efficiency?
I am trying to pull this next question out of research I did a year ago but...I believe the recoupaerator transfers some latent heat or humidity from outgoing to incoming air....is this due to the cross flow leakage? I remember this transfer being a feature that was advertised as a selling point so was the 10% leakage a design flaw or intentional?
Furthermore (that always sounds so combative...but in an attempt to make better transitions, not use "also", or a preposition that is what we get =) doesn't the HVI testing try to adjust for crossflow leakage, motor heat, etc. in their numbers to provide apples to apples comparisons? I am surprised that they would allow that to go through without adjusting the numbers accordingly otherwise their testing doesn't really mean anything....we might as well just take the manufacturers at their "word".
One further question (I know I could look it up...but refer to my comment about my wife earlier): what is the lowest cfm setting of the Zehnder residential products? Barry was using numbers at 100CFM and I am wondering if that is the bottom range for most of their products....100cfm continuous is overkill in most houses ( Thank you very much for your time,
Spencer
Spencer,
Barry Stephens is smart and honorable. But keep in mind that he is also a Zehnder distributor.
I am not sure exactly what you are cautioning against Martin. I am only asking his opinion of a product that is in competition with his and other relevant questions concerning his product and the workings of it...I am assuming he is smart and honorable and would give me information based on his knowledge of the subject matter at hand. That is why I am asking him. Obviously though I am talking to people on the internet and one can say whatever they want to...so naturally I would seriously inspect any information I was given...I feel like I am talking as if I am in The Princess Bride..."Naturally one would assume....because only criminals come from Australia...therefore....Your logic is flawed!"
Thanks,
Spencer
Spencer… I’m sorry, this is going to be long- but here we go
HVI is a listing agency. Not a test agency nor scientific body. The testing protocol to which all north American residential products are tested to- is standard CAN/CSA C439. We manufacturers have product tested, third party, to C439 and then choose to list those results with HVI, or not. We currently do not see the benefit from being listed there. The testing we have is the same as all other product listed with HVI and can be found on our website.
C439 measures the impact of outside air after energy exchange as it would affect the building conditioning load. Primarily focusing on duct 1 (outside condition), duct 2 (air conditions entering the building) and duct 3 (building room condition which you want to maintain). Why care about the energy leaving the building. To calculate a building load- you want to know how much mass flow of colder/warmer more humid/less humid air you have affecting your inside set condition. What I really want to say is- both test protocol have equal merits and can easily be argued from both sides. Moot point.
We do have- as noted- exhaust air contamination, or ‘cross leakage’. However, our testing numbers already reflect this penalty in performance due to cross leakage. C439 test protocol calculates efficiencies and incorporates the penalty associated with cross leakage. For instance- we had product tested in Europe, under a different test protocol in which we had less than 3% cross leakage which resulted in 98% sensible transfer [ASE]. So, with less cross leakage our product would be more efficient.
Looking at cross leakage from a different angle- most competing units have a function called recirculation defrost. So- when the outside air temperature drops below their ‘frost’ threshold, usually 28 F, the unit will stop and/or lower the amount of fresh air coming in and replace that with the leaving stale air in order to keep the core from freezing. If I may say- this sounds like 100% cross contamination. Cross contamination is a harsh description for say ‘less fresh air coming in’. It merely means that if you thought you were bringing in 100 CFM, and you have 5% cross contamination- you are really brining in 95 CFM of fresh air and 5 CFM was just recirculated. Note that your forced air furnace is 100% cross contaminated or recirculated air. The objective with ventilation is to change some of the stale inside air for fresh outside air- roughly in the amount of 0.25-0.3 air changes per hour at the lowest ‘cost’ to you. With regard to defrost- we have tested that modulated heat is the most efficient solution. Solar thermal/geo loops/electric resistance… you choose. Most are also an offering from Zehnder also.
On to fan efficiency. When comparing fan efficiency- you must ask at what filtration was the air delivered at. Our product was tested to C439- with a MERV 12 filter in place. Filtration adds to fan power, and C439 protocol does not specify you must provide information on nor test with any filtration. Our flow ‘sweet spot’ is between 60-80 cfm- where we use around 45 watts depending on duct restriction. I am not sure what filtration the Zehnder unit had installed while being tested.
HRV/ERV. It is understood that there are significant costs to be saved when moisture transfer is in play with an ERV. There are few north American climates that will not benefit from an ERV versus an HRV. Note that Zehnder has only an HRV listed- which is less applicable to most of north American climates. Latent performance coefficient dictates how much humidity will be blocked from coming in [on a hot/humid summer day] or retained in the home [ on a cold dry winter day]. There is a significant concern with passive house and summer humidity which Germany is unfamiliar with and north America is struggling with. But for sure- under this condition you want an ERV with the highest latent performance coefficient [LPC] as possible. Zehnder did not have this part of C439 testing done, and only listed an HRV. UltimateAir’s LPC is 0.43% (among the highest in the industry). Water removal or addition to an air stream generally costs 3-4 times more than heat[sensible]- so it is important to pay attention to this performance detail.
Flow control. Note that our testing shows the same air flow [CFM] at different duct restriction conditions. Long ago we learned that ERV’s were getting a bad rap because units were getting installed and not flow balanced- or becoming flow unbalanced over time. So we fixed it with independently controlled constant flow fans. We implemented this back in 2004.
Noise. Most noise is mostly attributed to installation. Poor installation – meaning high velocities/restrictions/ and/or poor acoustic decisions when ducting will lead to noise. I always recommend staying below 700 fpm- duct velocities and using three feet of insulated flex duct to start all runs at the point of contact with the unit. There are many other factors- but if these two things are done there is usually no issue. Zehnder will sell you some very high cost duct mufflers (which would work with our units also) if the duct installation is transmitting noise to the house. I prefer to recommend the right ducting versus the duct muffler ‘Band-Aid’. That said- noise will continue to plague any and all mechanical equipment. Plan accordingly.
US building code generally requires product to be UL1812 electrical safety certified for installing product in the United States, and for Canada you need CSA C22.2. UltimateAir has both. I’m not sure if Zehnder has these? Maybe someone can find out- I only see CE on their literature with is for Europe.
The UltimateAir unit is variable flow- anywhere from 30-200 CFM. Ventilation is generally recommended to be operated continuous (best practice)
In a nutshell- UltimateAir and Zehnder make a good product. An unbiased engineer with this type of experience will most likely tell you that calculating the difference in savings when looking at these two manufacturers is going to be tough and probably show very little difference. The choice remains- the much higher priced, imported, overseas product- or the USA made product of equal caliber that you are not paying to transport from a different continent…. Good luck -and UltimateAir will respect your decision.
Jason Morosko, CPHC
VP Engineering
UltimateAir Inc.
PS- I recently built my own passive house, see it here is you want http://www.sustainablepath.us
in terms of unit price - we found that the 200dx and the comfoair 200 weren't exactly worlds away in terms of cost. zehnder's proprietary and uber-cool ducting is where the cost difference lies - but it's not necessary.
WRT Passivhaus, the 200dx is at a significant performance disadvantage. first, as it's not certified (zehnder's products are cert'd through PHI) there is a 12% deduction in heat recovery (note - with the new protocols, that deduction increases, to 18% IIRC).
i'd love to see the 200dx get cert'd - but i'd also love to see zehnder fabricating its products here in the u.s. - and last i heard, they had been exploring that.
Okay, let's run this exchange just a little longer. Good information being shared.
Jason, you have CPHC behind your name. And you said "Why care about the energy leaving the building." Really? Does that mean the higher R-values for walls and roofs doesn't matter? Or those very expensive triple glazed windows from Europe with low U-values don't matter?
FYI, we tested the CA 350 for the -25C test with HVI using a 800 watt modulating pre-heater. We got 99% ASE. Is that all that matters? Not at all. We used a lot of watts, and the exhaust air stream expelled a lot of energy to the outside. The lab corrected that in the SRE number, but from the perspective of PHI or PHIUS, the percentage of the heat expended to pre-heat the air coming in that ended up on the exhaust air stream is huge. And cross-flow leakage plays a very big part in PHI certifications.
We will be testing the ERV version of the CA 350 in coming weeks, and the results will go up on the HVI website for the 1 January 2013 listing. They do the listing every quarter. Additionally, PHI now does test ERVs, and the CA 160 is certified for both the HRV and the ERV model. We will have the certificates at next week's PHIUS conference, as well as up on our website shortly. This is the first ERV to have been tested to the PHI standard. Now that PHI does ERVs, we will look forward to seeing the results for the Recouperator.
Zehnder has been working to list with UL/CSA, and our first model will be in production shortly, with additional models coming quickly after that. And yes, we will ultimately manufacture here. But keep in mind, the carbon footprint per unit to ship one unit from Ohio to Seattle or San Francisco on a truck is greater than shipping a container of units to CA or Seattle direct from Rotterdam. Which is what we are doing now in CA, and shortly in Seattle.
First I want to say this is really great. I am super happy with how this has went so far...it was actually exactly the discussion I was hoping to hear. Pretty much a nuts and bolts of why and how.
To Mike: I purchased a 200dx last November...it's still sitting in my attic uninstalled because I haven't reached that point yet...but that's another story...the basic unit with no frills was significantly cheaper enough to me at least to justify it. In the spirit of PGH the 200dx seems like a good deal, but if you added all of the extras that would be nice to have like a dehumidistat, co2 sensor, etc. you would definitely get up to the cost of the Zehnder really quickly. If I remember correctly the Zehnder comes automatically with pretty fancy features (like those I mentioned) and control mechanisms that I would certainly love to have. Huge metal ducts, mastic, and machine screws seem really really silly to me as well and the comfotube certainly looks like it would kill all of that.
I have wondered for a long time why people haven't been using PVC pipe for HRV runs. Does it create static or is it simply just not something people do? I know one contractor that tried once and the inspector told him he had to rip it all out....but I know a lot of inspectors and if one thing is true about them it's that they don't like anything they have never seen before. Again the comfotube would be even easier.
So one more time, thank you for all the info. If I can ever talk someone into installing one of these in a house that would actually benefit from one I will have some great information to bring to the table.
Spencer
"I have wondered for a long time why people haven't been using PVC pipe for HRV runs."
I suspect it is not code approved for HVAC, possibly due to concerns about off-gassing. Concern has been raised regarding off-gassing of PVC flooring, so passing all your ventilation air through ducts made from it is definitely questionable.
Installers have been using thin-wall PVC pipes for HRV ducts for many years -- but usually only for exhaust ducts, not supply ducts, because of off-gassing concerns.