GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted
Musings of an Energy Nerd

A ‘Magic Box’ For Your Passivhaus

Can Americans buy a combination appliance incorporating an HRV, heat pump, and water heater?

This HRV hides an air-source heat pump. Nilan HRVs from Denmark include an air-source heat pump that recovers heat from the ventilation exhaust stream.
Image Credit: Nilan

UPDATED on March 13, 2015

By designing a tight envelope with thick insulation, Passivhaus designers work hard to whittle a home’s space heating load to a bare minimum. Many European designers strive to get the heating load so low that all space heat can be provided by raising the temperature of the ventilation air.

In a home with an area of 1,600 square feet and a ventilation rate of 0.3 ac/h, ventilation air flow is only 64 cfm. Since Passivhaus designers try to keep the temperature of the ventilation air below 122°F (or, according to some sources, 131°F), it’s hard to pack much heat into the small volume of air that flows through typical ventilation ducts. That’s why it’s such a challenge to insulate a building’s shell well enough to deliver all of a home’s heat through its ventilation system.

In central Europe, where winter temperatures are much milder than they are in Minnesota or Maine, some designers have succeeded in supplying all of the space heat needed for a Passivhaus through ventilation ducts. In most cases, these homes are equipped with a “magic box” — the nickname for a combination appliance that includes a heat-recovery ventilator (HRV) and an air-source heat pump. Typically, the heat pump’s evaporator coil is located in the ventilation exhaust duct, downstream from the HRV, where the coil can scavenge heat from the exhaust air before it leaves the building.

Many (but not all) of these magic-box appliances also include a hot water tank. Such appliances use the air-source heat pump to heat domestic hot water; in most cases, the tank includes electric-resistance backup. Some manufacturers (including Zehnder) design their magic-box appliance around a ground-source heat pump instead of an air-source heat pump.

Magic boxes in North America

I’ve heard rumors that magic-box…

GBA Prime

This article is only available to GBA Prime Members

Sign up for a free trial and get instant access to this article as well as GBA’s complete library of premium articles and construction details.

Start Free Trial


  1. Chad Ludeman | | #1

    Adding boost to Ventilation for higher BTUs
    Great article with hard to find information and pricing in the US. I just wanted to add that UltimateAir (and probably others) are looking into offering an efficient boost fan that would increase the CFM's running through the ventilation ductwork without increasing the actual ventilation air. This would allow one to place a heating/cooling coil inline with the ventilation ductwork and deliver the needed BTU's without over ventilating the house.

    We haven't tried this yet, but are looking into the combination of this system with Daikin's Altherma system. The main problem with Altherma now is that their smallest units are 38k BTU and we require only 12k - 18k BTUs for our homes.

    One last note is that these combination systems that include water heating also lend themselves very well to adding solar thermal panels as the primary heat source to the water heating tank. This way, free solar energy is your primary domestic hot water heating source, the heat pump is your secondary source and the electric coil is the final fail safe. Not a bad little setup that will greatly reduce the size of a PV array for those looking to go Zero Energy or Zero Carbon.

    Keep it up!

  2. Ken Levenson | | #2

    We looked at using Altherma in a PH in Brooklyn - all electric and easy thermal solar integration made it very attractive. But we got nervous about elec coil for DHW in winter. Glad to hear the Maine home elec bills are low. Any idea about how much hot water are you using? (I've got a family of four and guests to contend with...)

    Also, in the summer, it is my understanding that the Altherma flips back-and-forth between AC cooling and DHW production - can't do it simultaneously.....more nervousness.... (we are nervous enough about hitting .6ach!)

    I really hope the system works - I'd love to take a closer look again at future projects - as PH seems particularly well suited, especially to the need for "flipping".
    I think the Altherma definitely deserves a good post on its own.

    Love the sound of what UltimateAir is looking to do - I hope they ramp up their efforts.

  3. Marc Rosenbaum | | #3

    Questions about the Nilan
    One of your best articles ever — lots of info and good analysis.

    So all the air flow in the Nilan is from outdoors, no recirculated air? My math according to their specs: 6,500 BTU/hr at a COP of 3 means the heat extracted from the exhaust air is 75% or 4,875 BTU/hr. at 175 CFM, this is a temp drop of 25.8°F.

    I wonder if they have a frost issue on the heat-pump coil or has most of the moisture been wrung out in the HRV? Do they say anywhere what the efficiency of the HRV is? Does the system change speeds as heating load increases?

    I'd like to understand the temperatures and energy flows throughout the system. When they say 6,500 BTU/hr, do they mean that energy is added to the building based on 70°F indoor setpoint, or to the supply air coming off the HRV which is below the setpoint of the space?

  4. GBA Editor
    Martin Holladay | | #4

    Excellent questions
    I hope a reader or a technical rep from Nilan will be able to answer your excellent questions.

    I asked some of the same questions in my phone calls to Solution Nilan, but our dialogue was somewhat hampered by the fact that English was not the first language of the rep I spoke with. I welcome anyone familiar with the Nilan unit to respond.

  5. Chad Ludeman | | #5

    Re: Altherma
    Ken - I spoke in more detail with the US rep for Daikin Altherma a few days ago. The average SEER on the cooling is 19 and this takes into account the switching from cooling to hot water. If you have solar thermal hooked up to your DHW, then there will be little need for supplementary heating in the summer by the heat pump and almost certainly not by the electric element. The Daikin unit has decent controls that allows you to control the functioning of this switching even further if you so desire.

    We currently have been using stand alone solar thermal systems with electric coil backups in Philadelphia (not too far south from you) with no detrimental effect on utility bills that would cause us to doubt this strategy either.

  6. Bjorn Kierulf | | #6

    Consider heat load
    Great blog! The main reason Dr. Feist champions heating by ventilated air comes from simplicity. The ductwork for heat distribution is allready existing, and adding some heat with a coil doesn't cost much.
    But it works only for heat loads of 10W/m2 or less (sorry, Í am from Slovakia, Europe, and not familiar with BTUs and sq.ft...). My experience is that our climate leads to heat loads of 13-15W/m2, for very small houses even higher.
    My solution has been to use drexel & weiss units for covering the basic load, and adding one or two electrical panels for covering the peaks. Works very well, ads a few 100 KWh/a to the electrical bill. But because the compact unit (magic box) covers ALL hot water, the overall consumption is low. In PH, you need more energy for hot water than heating.
    Some recommendations:
    - In cold climates never install a unit with a higher min. air exchange than 0,3 1/h. It will lead to dry air imdoors
    - concentrate on covering hot water demand efficiently
    - cover the peaks by 1 or 2 electrical panels
    Now, new compact units do separate heating from air flow. The XLS from d&w does so partially, the X2 gives all heat to a low temp. heat. system. The efficiency clearly increases, you can lower the airflow in winter and X2 can provide passive cooling as well. This concept has no functional drawbacks, but a longer sub soil coil (thats where the heat and cold is coming from) and a low temp heat system adds to the cost.
    After two years of measuring our first PH, the overall consumption of the whole house was 4600KWh/a. The floor area is 170m2 with XLS installed. We later found out that a smaller circulation pump could have saved us another 600 KWh/a - it runs winter and summer, to defrost and to cool.
    Now we are working on a very small PH (88m2), and a compact unit disqualified itself. Their air exchange is too high or the XLS and X2 are overkill. So we go for solar hot water and very efficient HRV from Paul.
    So you need to adapt the system not only to different climates (for milder climates the airbased compact units are just ideal) but also to size and number of occupants, because of varying hot water demand.
    I will have more about our projects on my blog, you can follow entries on Twitter, username: createrra

  7. Ken Levenson | | #7

    Thanks, Chad. I agree - it should all work.... Once I get this first PH under my belt we'll go back and take another look.

  8. Nick | | #8

    I have a Nilan VPL-15
    I have a Nilan VPL-15 installed in my house located in CT and I have been fairly happy with it. Even though I don't quite have passive house levels of insulation (r32 walls, r60 ceiling, window U value .17-.2) the unit takes care of some of my heating needs, I am still using spot heating via electric resistance for backup.
    I am not an expert on the unit but I can share what I have observed since installing it in Dec of 09.

    As far as i understand the Nilan vpl15 does not have a typical heat exchange core coupled with a heat pump, its only means of recovering heat is through the heat pump. Prior to buying the unit I was under the impression that it had a heat recovery core AND heat pump, but Im afraid i was mistaken. There are temp sensors in various parts of the machine (outside air, indoor air, condenser temp, evaporator temp, and inlet air). When the heat pump is not running (just the vent fan) the inlet temp is more or less the same as the outside air temp. So when the heat pump isn't running at 500w and hour, you aren't getting any heat recovery.
    The unit does go into defrost mode intermittently at low temps, but Ive overcome the need to do this by running a short ground loop w/ a heat exchanger in line with the fresh air. Even on the coldest nights (5f) I never saw fresh air temps below freezing.
    No the unit does not change flow rates when the heating load increases. You basically set the ventilation rate you want (there are 4 steps) and it will adjust the inlet temp to match the desired room temp.
    From what I understand the 6500btu is a number based on energy added to the supply air not the 70deg indoor air. For example, during the winter I had airflow set to around 100 cfm and would have a fresh air reading of 32f(real temp was far lower because of geo heat exchanger), an indoor temp of 70f, and supply air temp of around 90f. Based off that flow and change in temp you can figure out the btus it produces.
    If I was to do it again I think I would go with a conventional high efficiency HRV and couple it with low temp mini split heat pump like the mitsubishi mszfe12na. I would get a higher capacity system, get decent heat recovery w/ low energy input, and probably still come in cheaper than the $5k price tag of the Nilan.... Basically Martin is correct, its ALMOST a magic box.

    As far as the Daikin Altherma, the estimate of $10k-20k instalked seems WAY off from the quote i received. For a 3 ton forced air system i got a quote of $36k(!!!), which was more than geothermal when considering rebates in my area. This would be the first system this company installed so maybe there was a considerable amount of "padding" to cover for any unknowns. Until the price comes closer to the $10-$20k price that Daikin estimates I cant see these units really taking off.

  9. Brad Rogers | | #9

    20,00 BTU Furnace?
    I have designed an energy-efficient, 1350 sf home that requires only 20,000 BTU of heating. I can't find a 20,000 ducted gas furnace on the market. Can anyone recommend one?

  10. Jan Juran | | #10

    Low BTU Gas Furnace
    Brad, check out the Goodman GMH95-045 model gas (natural gas or LP gas) two stage condensing furnace, 95% AFUE with an ECM blower motor (descriptive info is at Either a multi-speed model or the variable speed blower model may fit your application. The Goodman is competitvely priced and comes with reasonable warranty terms.

  11. Russ Hellem | | #11

    Low Btuh Gas Furnace
    York Manufactures a fully modulating 98% AFUE condensing gas furnace that modulates down to 21,000 btuh. It is one of few will full modulation, most of the manufacturers have several stages, this model actually has 100 different stages and an ECM blower.

  12. Andreas Benzing | | #12

    I researched the HRV with
    I researched the HRV with integrated heat pump because in a project for a Manhattan apartment we are not allowed to place a condenser unite on the outside. This means an integrated solution at least for cooling and fresh air is needed. I found two danish companies which offer what I need, both where interested in the US market and I also had a conversation with Reinhard Weiss the CEO of Drexel & Weiss and his company will offer the products by 2012. I personally did not think Nilan has the right aswer since it does not integrate a counter flow HRV.

  13. Jason L | | #13

    Tankless hot water heater + Hydronic heat exchanger?
    Great Post, thanks for the info.
    What about using a new Rinnai Tankless hot water heater and one of their water-air heat exchangers? &
    (RC80HPi is 96% efficient)

    Doing a bit of research online it looks like this combo is $2,400 (RC80HPi $1,400 + 40k BTU exchanger 1,100) not including installation. One could then combine this will a traditional HRV and AC coil if needed and have a really nice system for under 4k not inc. install. It seems like solar thermal with a heat exchanger tank could also be included with this type of setup?

    I came across this as I have one of their older tankless hot water heaters (unfortunately only 82% efficient). I'm quite happy with it, plenty of water for shower, bath, dishwasher and laundry at the same time, even on the rare but experienced -20 January night here in Minneapolis. What is really nice is that the unit is double sealed combustion with the outside air intake around the exhaust so no chance of any fumes leaking into the house.

    I have an existing forced air furnace in bad need of an upgrade, but want to spend money on insulation in my renovation an not buy an expensive furnace -- I think the water-air exchanger would be a nice way to go for about 1k + a new HRV? I would have the possibility of a future upgrade to a new 96% efficient unit sometime down the road and/or solar thermal integration? This would use all of my existing ductwork and AC coil. It also seems like I am getting the best efficiency out of every component, 96% Nat gas for heat & water, no tank waste and the ability to get the best HRV set for ventilation needs plus future solar possibility. It would use all existing (and some new) ductwork to deliver heat/cool/ventilation to each room in the house.

    Might this also be a good economical option for an efficient, but not quite passive house std, home?

    I did look into air heat pumps, It seems they hardly work it all when it is below 0 which is when I would need heat the most. I would think natural gas would be better then simple electric resistance (as here in MN we are half coal. I do buy all Wind power from Xcel (only $3 more per mo!) but that doesn't mean a future owner would buy wind. Ground source not really an option due to tight city lot and tight budget... I further thought of a wood/pellet stove, but what about that time when I am on vacation and it hits 0 degrees...

  14. Steve Tjiang | | #14

    Nilan VPL-15 for near-passive-house-standard Home
    I am building a "near-passive-house-standard" Home in Northern California. We're considering the Nilan VPL-15 as a combined HRV/space heating appliance.

    I don't doubt the Nilan VPL-15 is very efficient in a european climate. Since it uses a heat pump w/o a passive HRV heat transfer core, the Nilan may be less efficient when temperature difference is low between the exhaust and fresh air streams. In the more moderate northern california climate the VPL-15 may be less efficient than a separate passive heat exchange HRV together with a separate heat pump. The latter would just be off when not needed while the Nilan heat pump needs to operate continuously to get any heat exchange.

    For Nick:

    I am looking at an HRV with a ducted mini-split heat pump. Do you have any recommendations about how to configure it?

  15. JustHousing | | #15

    When the answer isn't a magic box
    Excellent article Martin. You seem to have sparked a conversation beyond whether or not the magic box makes sense in low energy homes, and into WHAT makes sense in very low energy homes. I appreciated your summary at the end of the pros and cons, and here in MN I've pretty much embraced all you list in the arguments against the Magic Box. But, as usual, the devil is in the details and I still struggle with the details, as more and more good products enter the market. As for the HRV, I currently favor the Venmar EKO1.5 and leave it at that. Most of the homes I'm dealing with have a peak heating load of 12k-20k Btu/hour and I'm typically using some kind of hydronic system with lower delivery temps. The biggest question I still face has to do with whether or not to combine hydronic heat and hot water heating and if so, how. Tank or tankless water heating? Modulating boiler with indirect-fired water heater using well-insulated storage tank? Totally separate systems - small boiler and separate hot water altogether? (For the moment I'm ignoring cases when we have a solar thermal component - those systems seem easier to solve than those without solar, since the it is better to unify a systems when storing energy from the sun.) For small homes with core-designed plumbing systems, I like the idea of condensing sealed combustion tankless water heaters. I think. The new Navien combination system for hot water and heating seems good, but I'm not an engineer and I'm not sure how to balance out cost, efficiency, and effectiveness. And how about elegance? Anyone care to offer up their favorite low-energy systems for hot water and hydronic heating? I shy away from electric because we're in MN, where it is very cold and very "COALED."

  16. AWR | | #16

    Nilan units for passivhouses
    Nilan is also able to deliver "magic boxes" the one mentioned in the link was installed in the winning house at Solar Decathlon 2009 and is participating at Solar decathlon europa.
    Only available as 50Hz 230V

  17. Kevin Dickson, MSME | | #17

    How 'bout three cheap magic boxes?
    I think the following appliance configuration is far more cost effective and simpler than anything yet proposed in this thread. (As in, about 5X cheaper than the Daikin). Since this forum is the great for finding flaws in logic, so have at it guys:

    Remember, Martin’s article discusses very low energy homes on the order of PassivHaus. That means a design heat load of, say, 10kbtuh.

    That small load can be easily met with a motel-style “Packaged Terminal Heat Pump” (PTHP). These cost under $700 installed. (They just plug in like a through the wall (TTW) air conditioner). Amana makes a good one.

    If you also want a heat-pump water heater, the Geyser can be installed outside or in the garage, so you aren’t cooling the house in the winter when you heat the water. $600 plus some plumbing.

    Let’s say this is a two story house, and you want an HRV/ERV. Use one Panasonic WhisperComfort Spot ERV on each floor, $600 total. That’s enough fresh air for up to 5 bedrooms, and no ductwork to install.

    Also remember that natural gas is usually not a good idea in these very low energy homes, so electric must be the backup source of heat.

    To date, I’ve only found one home that has used a PTHP as the primary heat source, but it was successful. Greg Lehman says, “Because the house is so compact and highly insulated, we eliminated the central heating system. The air source heat pump, which is like one found in a hotel room both heats and cools. Heat in the lower level is provided by small baseboards in the bedrooms and an electric heater with a fan in the bathroom.

    We tracked the performance of one unit from February 1st 2009 to February 1st 2010. The cost to heat the unit came to $185.24 which averages to $30.87/month or $1.03/day. The square footage of the unit is 1150. A separate meter which tracks electric used by the heaters showed 2795.5 kwhs used during the six month heating season of mid-October to mid-April. “

    PTHP drawbacks:

    1. They are noisy. That doesn’t really matter because it doesn’t need to run often in this house.
    2. The COP is low during cold spells. I’ve done Energy Plus thermal modeling, and the electrical resistance heat only comes on for a few hours per year in Denver.
    3. The COP of a PTHP is low compared to a minisplit. Yes, but so is the first cost. After a few years when they start putting ECM powered fans in the PTHPs, you can upgrade easily, and sell your old unit on Craigslist for $200.

    Small superinsulated homes like these tend to stay isothermal. That means you don’t need distribution ductwork, just leave doors open as needed to even out the temperatures.

  18. GBA Editor
    Martin Holladay | | #18

    Response to Kevin
    An excellent suggestion.

    For me, the deal-breaker would be the noise. But I love the idea of simple and cheap.

  19. Peter Sønderskov | | #19

    The right Nilan unit for a true Passive House
    Nilan A/S, Nilanvej 2, 8722 Hedensted, Denmark, Phone: +45 76 75 25 00, Fax: 76 75 25 25,

    Press release

    2November 2010
    Danish manufacturer of ventilation and heat pump technology receives internationally recognised passive house certification
    The Danish company Nilan A/S that specialises in energy-friendly ventilation and heat pump solutions has received the internationally recognised Passive House Certification for its VP 18 Compact P system. Nilan is the third manufacturer of compact systems in the world to achieve this, and the certification thereby proves Nilan to be among the elite of the ventilation and heat pump industry.
    1 November 2010 saw the presentation of the internationally recognised Passive House Certification from the Passivhaus Institut (PHI) in Germany to the Danish company Nilan A/S. Nilan received the certification for its VP 18 Compact P, which is only the third compact system in the world to be given this recognition.
    A compact system combines the technologies of active and passive heat recovery, ventilation, heating and cooling of a building, as well as heating of domestic water. With the certification, PHI recognises the VP 18 Compact P system’s efficiency and thereby also its lucrative life cycle costs, high cost effectiveness and not least its high COP (Coefficient Of Performance), thereby giving the seal of approval for the system to be used in passive houses.
    Took the best and made it perfect
    More specifically, the certification shows that the VP 18 Compact P is accepted as a suitable solution for integration in passive houses, and that its efficiency does not need to be checked further by the construction team. In other words, the system can be installed in the house and its data integrated without further calculations and documentation in the energy calculation system forming the basis of the construction and of the house’s status as a passive house – a system that is developed by PHI. This simplifies the planning process and guarantees the product’s efficiency.
    – We never cut corners. The VP 18 Compact line’s key product was a candidate for the certification even before we decided to develop it further and upgraded it to VP 18 Compact P. However, we wanted the certification to be assigned to a product that is not just good but pushes back the boundaries. So we took a strong product and made it perfect. It took us two years, during which we implemented the improvements in the system as the work progressed, but it was worth the time and efforts, and we are very satisfied with the result, says Nilan’s Export & Marketing Director Peter Sønderskov.
    Pat on the back by the institution leading the way in the low energy industry
    PHI is an important actor in the market for low energy buildings, not least due to the fact that the institute created the passive house concept. PHI sets the standards as to what is required in terms of energy consumption in passive houses. The institute is thus also a trendsetter for future EU requirements for low energy buildings.
    PHI’s work includes evaluating whether specific products are suitable as components in passive houses, based on accredited test results. A sign of approval from PHI therefore carries weight and emphasises the receiver’s ability to create solutions whose energy consumption places minimal strain on the environment and the owner’s heating bill.
    Nilan A/S, Nilanvej 2, 8722 Hedensted, Denmark, Phone: +45 76 75 25 00, Fax: 76 75 25 25,
    Contact information
    Peter Sønderskov Export & Marketing Director Phone: +45 40 19 22 25 [email protected]
    • The VP 18 Compact line was launched in 2006 and has become one of Nilan’s most popular product lines within the last four years.
    • Passiv Haus Institut (PHI) in Germany developed the passive house concept and defines the requirements a house must meet in order to be recognised as a passive house. Learn more at and
    • A passive house uses a minimum of energy, as it is built with the purpose of retaining and utilising the heat from the sun, among others, as well as recover the heat in the house by means of a ventilation system with heat recovery to a much larger extent than traditional buildings. This reduces the need for heat supply to a minimum and consequently also the heating bill, and you get a more healthy indoor climate, while protecting the environment at the same time.
    • Both new buildings and renovation projects can be built as or upgraded to passive houses.
    About Nilan
    Nilan develops and produces energy-friendly ventilation and heat pump solutions of the highest quality which ensure an outstanding indoor climate and low energy consumption in consideration for the environment for both the domestic and commercial sectors.
    The internationalisation of Nilan has been increasing steadily since its founding in 1974. Today, the company is represented in the majority of the European countries.
    Nilan A/S, Nilanvej 2, 8722 Hedensted, Denmark, Phone: +45 76 75 25 00, Fax: 76 75 25 25,

  20. GBA Editor
    Martin Holladay | | #20

    Response to Peter Sønderskov
    Peter Sønderskov,
    Thanks for the information, Peter. When I wrote the blog on April 16, 2010, I mentioned the VP-18, but it was not available in North America.

    I just called Richard Grant again at the Nilan distributorship in Chambly, Quebec, and he said that the VP-18 is still not available on this side of the Atlantic. So your information is useful for European readers -- but unfortunately, it won't help U.S. or Canadian builders until someone decides to distribute the VP-18 over here.

  21. Daniel Simard | | #21

    Nilan VPL15, great machine
    Hi to all of you,
    I bought from a VPL15 from Richard Grant in 1997, it's been running flawlessly since april of 1997.
    Living on the south shore of Montreal, i just started heating the house with the central unit last week.
    It's gives an idea of the heating potential of the machine.

    I found another VPL15 in the classified ads and it has almost never run.
    I'm willing to sell it, write to me!

    You can't go wrong with this machine...

  22. alakazaam | | #22

    magic boxes in europe
    Hi I hope you do not mind me adding to your discussion. I have invented my own magic box. It has taken 3 years. My product is actually called the Magic Thermodynamic Box. This box is a cross between an air source heat pump and a solar thermal type system. The good news is that I designed out the noisy fan which guzzles electricity with an atmospheric evaporator panel so no noise and achieve hich COPs of 1 in 7. Also works down to minus 15 degrees. further info We have been installing about 60 daikin althermas a month in the uk Our government has put an incentive on them to help with the purchase cost. However my experience has been that as soon as we try to get to the high tempretures over 65 degrees we have found that they consume huge amounts of electricity and the COP performance from our calculations are 1 in 0.65. This means that it would be better to run your standard boiler which is 1 in 0.8 COP So we have now come up with the Magic Heating box which along with the Magic thermodynamic box is world wide patent protected. This actually retrofits to your existing boilerand reduces the output from the usual 80 degrees to 60 degrees and yet your home heat will feel much better and save you between 30 and 50 percent of your bill. If you get time look at there are 3 videos there showing how the system is installed. All we need now is an American distributor so you guys can save too

  23. user-1068185 | | #23

    High ventilation rates-is 500 cfm really too much?
    Wouldn't a high ventilation rate be a good thing if one has to have air pass through lots of filtering media? Maybe people in Maine have good quality outdoor air, but that's not true of a lot of places in the U.S. Maybe it was overkill, but I know of a man on the West Coast in 1995 built a home with radiant hot water heat in the insulated slab, with not only a HEPA filter, but also 1,000 pounds of activated charcoal to filter outdoor air pollutants (car exhaust and neighbors' wood smoke).

    He changed the filters every nine months. The house was large, nearly 3,000 square feet. He had severe multiple chemical sensitivities. I don't know what his ventilation rate was, but the ductwork was huge and took all the space in the attic. After a while, the family stopped the 24/7 continuous ventilation to only 12 hours per day to cut costs. The house was located in mild climate of California's South Bay area where the summers are cool and it never freezes.

    I'm just saying, maybe some people, for reasons other than heat, need higher than normal ventilation rates.

  24. GBA Editor
    Martin Holladay | | #24

    Response to Barbara A. Smith
    Q. "Is 500 cfm really too much? ... Maybe some people, for reasons other than heat, need higher than normal ventilation rates."

    A. This is a free country, and if anyone wants to set up a 500-cfm ventilation system, they are free to do so. However, they had better have a fat bank account, because a 500-cfm ventilation system will use tremendous amounts of energy: first of all, energy to run the powerful fan; and second, energy in summer to cool and dehumidify the huge volumes of air, and energy in winter to heat it.

    Most single-family homes require ventilation at rates ranging from 40 to 90 cfm.

  25. capitainexl5 | | #25

    A magic box called Boreal 12000
    I have recently stumbled across a product I wasn't aware of that seems to be an evolutionay step from the other machines described in this blog. It is called the Boreal 12000 from a company named minotair. It has quite some decent juice in terms of BTU (heating and cooling) and has several modes of operation. It even has constant airflow blowers with variable speed allowing for modulation and realtime balance of the intake-exhaust airflows. Its airflow range is 80 to 250 CFM which won't over-ventilate your home. The company is based in Canada but they sell in the U.S. as well. Might be worth a look ( Has anyone ever tried this machine? I plan on making a phone call to minotair and learn some more...

  26. GBA Editor
    Martin Holladay | | #26

    Response to John Deburg
    The link you provided doesn't work -- at least on the day I clicked it -- but here is a link that is working: Minotair Boreal Model 12000.

    And another: Specification sheet.

    There are some unanswered questions -- I need to do some more digging. While the literature claims that the unit provides heating capability, I don't think that the heating is provided by a heat pump. The literature notes, "A self-contained design requiring no installation of outdoor equipment for greater aesthetics and unparalleled ease of installation and maintenance."

    Obviously, the heat pump can't extract any heat from outdoor air unless there is outdoor equipment.

  27. capitainexl5 | | #27

    Response to Martin Holladay
    Good point Martin!
    But I think they just meant that there is no outside coil equipment to install outside. Obviously, one would need to install air intake/exhaust hoods, which would be apparent just like any other HRV/ERV.

    Planning on calling them Monday to learn more. By the way, the link worked for me today... maybe they had some maintenance going on...
    Found this guide for download off their site too: User Guide

  28. user-1017420 | | #28

    Minotair Boreal 12000
    Hello John,

    Did you ever find any information regarding this machine?
    I'm not sure what to think of it??


  29. propeller | | #29

    Minotair Heat Pump
    Hi Alec,
    To me, it seems like if the inside of a Minotair is very similar to a Nilan.
    Basically it's an HRV where the heat exchange is done through a small reversible heat pump versus a typical HRV core. Picture a regular heat pump but instead of locating the heat exchange coil outside of your house, you locate it inside and instead bring the outside air to it. It's actually much more sophisticated than that.

    I've lived with a Nilan for many years in a previous house but in retrospect these self contained heat pump/HRV are expensive and complicated product that few people can repair. It's cheaper to repair or replace a regular HRV and a minisplit. My two cents.

  30. Griffin728 | | #30

    So still no good low cost options?
    It's been over 5 years since the original article, but I'm not seeing any good options for what otherwise seems like a great idea. Is there anything else in this space that I'm missing?

    Since I super-insulated my home without changing original HVAC, I'm left with very oversized furnace and central AC units. I really need an HRV because the house is so tight. It sure would be nice if there were a device to ventilate the home while also providing more constant and efficient heating and cooling for ~9 months a year while keeping the big units as backup. Plus I really hate the look of mini split units on the wall, and this would be all hidden and distributed. I'm not looking to integrate water heating at this time.

    Is there anything else that fits this need at a reasonable cost?

    Ryan Griffin
    Minneapolis, MN
    1,450 sq ft.

  31. GBA Editor
    Martin Holladay | | #31

    Response to Ryan Griffin
    I've written two articles on this topic since the article on this page was written. You didn't mention those articles, so I'm not sure whether you have read them. Here are the links:

    A Balanced Ventilation System With a Built-In Heat Pump

    Another North American Magic Box

    Most North American builders in your predicament are still installing separate appliances for ventilation and space heating -- for example, an HRV and one or more ductless minisplits. There are advantages to this approach, especially when it comes to maintenance and repair.

Log in or become a member to post a comment.



Recent Questions and Replies

  • |
  • |
  • |
  • |