Hydronic heating through the HRV supply air

[Danjoh99]

These are products I'm considering that deliver space heating through
the supply airflow. The heat source is the hot water heater. The
heat gets into the airflow using a hydronic coil (like a car
radiator). In Europe they can buy a compact heat-pump unit that does
all of this in one package. In the U.S., we've had to cobble this
together from different parts. Some complete products are now
available that also incorporate the ERV/HRV.

1. NTI (Nyletherm) Matrix. Complete ERV, condensing gas hot water
heater, and hydronic coil.
http://www.ntimatrix.com/solution.html

2. Lifebreath Clean Air Furnace. ERV and hydronic coil, but supply
your own hot water.
http://www.lifebreath.com/en/consumer/products/residential/caf/

3. Nuair heat recovery air handler. Like the Lifebreath, supply your
own hot water.
http://www.nu-airventilation.com/Single%20family%20dwelling.htm

4. Turbonics, Inc. HDX-17 and HDX-34. These are hydronic fan coils
that would fit in the supply airflow from the HRV. Designed for 120ºF
water. John Mann at HeatWave Radiant Supply in Ceres.
john.m...@comcast.net

5. Atrea "Duplex RK2". Designed for passivehouses. Incorporates the
hydronic coil into the HRV like #1-3 above. This is one of dozens
available in Europe, but available in the U.S.? Most likely not.
http://www.atrea.co.uk/en/heating-unit-ventilators

George points out that the first three products are designed for
heating loads much higher than for a passivehouse, so the components
are oversized and need adjustment to fan speed and water flow rate or
temperature. Number four could also be tailored to a passivehouse
load.

Is there anything else available off-the-shelf? Is it worth shipping
a heat pump unit from Europe? (The refrigerants are different--they
use propane!--and the voltage is different.) While we're dreaming,
why not import this one:

6. NIBE Fighter 410P. Complete ventilation with heat recovery, hot
water, and space heating in one refrigerator-sized appliance.
http://www.nibe.eu/Domestic-heatingcooling/Exhaust-air-heat-pumps/Product-range/FIGHTER-410P/

[Graham Irwin]

People in the US drool over the Passive House "magic boxes" that are
available in Europe (justifiably so.) My understanding is that
importing them is not an option. Apparently the frequency difference
(50Hz vs 60Hz) between US and European power causes them to catch fire
here!

Mike LeBeau at Conservation Technologies (http://www.conservtech.com/)
has done work on this with Passive Houses in Minnesota. Apparently,
there are some companies (USA coil and air http://www.usacoil.com/)
which make fan coils to spec - George is correct that most
"conventional" systems are oversized for PH.

It is important to compare the efficiency (both heat recovery % and
electric consumption) of the HRV units. My understanding is that the
Recouperator is the most efficient unit in the US market, on par with
European units. Many US units are far less efficient.

Graham Irwin
AIBD, CPBD, CGBP
Remodel Guidance
415-258-4501

Residential Design • Plans & Permits • Green Building • Period
Homes

[George J. Nesbitt]

The NTI (Nyletherm) Matrix looks pretty good. Back in the day
Lennox? had a condensing water heather with hydronic air handler built
in (the Canadians may have had one too). There was a U.S. company that
had a HRV hydronic air handler combination (John Bower, Ventilation,
1995 shows it).

I could not find electrical data for the Matrix, but it can run as
low as 300 CFM on heating, with a heat output of 12,000 Btu/hr at 180deg
F water temperature. This gets us in the range of heat loss. Nabih's &
David Gerstel's houses are in the 12-15 kBtu/hr range (my house as well
when done), Manual J, or ASHRAE 90.1. Although the PHPP would show
5kBtu/hr +/- roughly (due to internal gains and less safety factor?

The Matrix, Lifebreath & Nuair all come from the Canadian
governments comfortable initiative. I was unaware of the Matrix, thanks
Dan! I knew they were being developed.

The matrix looks like a Munchkin boiler with a HRV & hydronic air
handler. And you can do DHW & hydronics (floor, baseboard, etc.). Looks
like a winner.

The downside? cost? no solar hot water contribution except for the
DHW. Upflow design only (Nuair also).

It's difficult when the loads get so low, I had to increase my CFM
on David Gerstel's house, so the smallest registers would work (barely),
not complaints, and were in our second winter! (2x6 24oc OVE framing).
Total energy use is close to the 120 kWh/yr/m2 (depends partly on source
energy conversion).

I'm not yet sure what the best system(s) are, but I've been working
on it.

[Babette Jee]

Dan,
Could you describe how the house will be used?
Who are the occupants?
How much are they occupying the house? home office?
Purpose of the renovation? and size?
Goals for the energy measures
Budget?
Thanks, Babette

I think it helps to understand a context...

[Graham Irwin]

George,

It is important to know the efficiency specs when comparing these
units. PHPP recommends a "counterflow" vs a "crossflow" heat exchanger
with a "energy recovery efficiency" >= 75% (PHPP 2007 manual, p. 14)
and typically subtracts 12% from the manufacturer's stated heat
recovery value (PHPP 2007 manual, pp. 29 & 87)

Also, the efficiency of the fan motors must be considered. Since this
unit presumably runs constantly, inefficiency can wreak havoc on the
source energy limit. ECM motors are probably the only option, and even
then I would check the ratings.

Again, the UltimateAir RecoupAerator is the unit PHIUS (and Nabih)
have used. It is probably wise comparing these other units against
it's specs: http://www.ultimateair.com/Ultimate_Air/specifications/house_unit_specs.aspx

Lastly, I have heard of people developing tempering systems with pex
tubing placed UNDER the slab and glycol run through a thermostatically
controlled pump and fan coil at the input to the HRV/ERV. It's a bit
like an "earth tube" tempering system, but without the condensation
and mold concerns. In many cases, getting the outdoor air to 50/60ºF
before it even gets to the heat exchanger can be a big help, winter
and summer...

Graham Irwin
AIBD, CPBD, CGBP
Remodel Guidance
415-258-4501

Residential Design • Plans & Permits • Green Building • Period
Homes

On Jan 12, 2009, at 8:17 PM, George J. Nesbitt wrote:

>

[George J. Nesbitt]

I agree, and all decisions on equipment and building systems should be made with the the PHPP informing the decision.

I'll pass on drooling over the European equipment, and stick to North American! and maybe some Japanese.

The HRV efficiency is 72% (12% will be automatically deducted because it has not been "certified" by PH, and is a problem as we bring PH to the North America). I have not found the electrical data, by I can guarantee you it is an ECM motor.

There is confusion about the PH "requirements", it has come up in my GreenBuilding Listserve recently, and even in our group. There are "Requirements" and there are "principles" or "guidelines". HRV is not "required" for PH, but I would say highly recommended.

I have read through page 56 of the PHPP manual. The 75% HRV efficiency and fan watt draw are "recommendations" for the central Europeans climate. Our task is to define the "prescriptive" "recommendations" for California's Climates.

[Graham Irwin]

George,

The HRV efficiency is 72% before or after the deduction? To which HRV are you referring? The Recouperator's stated efficiency is 90%, which is why you get to 75% with deduction. Many US products aren't even close to this level, don't ask me why, I'm sick of speculating on that.

The ONLY requirements of PH certification do not include HRV, they are:

15 kWh/m2a maximum heating and cooling demand

120 kWh/m2a maximum total source energy

0.6 ACH @ 50 Pa maximum air leakage

Everything else is a recommendation, which is the beauty of the approach, IMHO - very "unprescriptive."

I am inclined to believe that an efficient HRV is important for reaching PH standard economically. I refuse to participate in the development of anything "prescriptive" for PH. I am eager to help develop proven and tested "best practices," "solutions," and "recommendations" unique to our circumstances.

Regards,

Graham Irwin

AIBD, CPBD, CGBP

Remodel Guidance

415-258-4501

Residential Design  •  Plans & Permits  •  Green Building  •  Period Homes

 

[George J. Nesbitt]

Matrix 72% (PHPP deducts 12% 72-12=60%)
Recouperator 95% (ERV, sensible + latent load, rated (95-12=84%)

I agree, minimal requirements, and flexibility on how you meet them is great. Our CA energy code is similar.

Sorry, maybe I should have not use the term "prescriptive", but many of the things people confuse as "requirements" are the list of "recommendations" for the central European Climate on performance thresholds that they may need to achieve to reach the "standard" or "requirements"

And our job is to define those "recommendations" or "guidelines" for CA and all 16 climates!

This sound too much like a PHPP discussion, we should start a "group" for that one!

[Stefan Carpentier]

Yes, I agree, a good and relatively narrow set of best practices, soultins and recomendations are what we need. As long as we structure them well so we do not confuse it more than necessary.

CIAO

              Stefan

[Danjoh99]

Hi All, I've uploaded a new diagram to the Group website. It shows
the draft mechanical configuration for our net-zero energy project in
Palo Alto. The file is called "Combi DHWspace heat
diagram_20090119.pdf" Here's a direct link:
http://phcdca.googlegroups.com/web/Combi+DHWspace+heat+diagram_20090119.pdf

I've sent this to a hydronic supplier for comments. I'd appreciate
anyone else's input. Thanks.

On Jan 12, 8:17 pm, "George J. Nesbitt" <geo...@houseisasystem.com>
wrote:

> > john.mann6...@comcast.net

>
> > 5. Atrea "Duplex RK2". Designed for passivehouses. Incorporates the
> > hydronic coil into the HRV like #1-3 above.  This is one of dozens
> > available in Europe, but available in the U.S.?  Most likely not.
> >http://www.atrea.co.uk/en/heating-unit-ventilators
>
> > George points out that the first three products are designed for
> > heating loads much higher than for a passivehouse, so the components
> > are oversized and need adjustment to fan speed and water flow rate or
> > temperature.  Number four could also be tailored to a passivehouse
> > load.
>
> > Is there anything else available off-the-shelf?  Is it worth shipping
> > a heat pump unit from Europe? (The refrigerants are different--they
> > use propane!--and the voltage is different.)  While we're dreaming,
> > why not import this one:
>
> > 6. NIBE Fighter 410P.  Complete ventilation with heat recovery, hot
> > water, and space heating in one refrigerator-sized appliance.

> >http://www.nibe.eu/Domestic-heatingcooling/Exhaust-air-heat-pumps/Pro...

[Graham Irwin]

Dan,

1) How is it that this house will be made "net zero energy" if you're
using natural gas? Will you apply some equivalency to excess
photovoltaic output which compensates?
2) You'll have to take steps to ensure that the potable water being
mixed with heating water doesn't cause health problems and/or building
inspector upset. My understanding is that some jurisdictions permit
this and others don't - the concern being that water in the hydronic
heating loop stagnates during non-heating periods.
3) I have heard reports (Gary Klein from the CEC a primary source)
that tankless water heaters are nowhere near as efficient as generally
assumed. The problem is that the device has to cycle for any hot water
draw, and most of the DHW draw in a typical home is in short "events"
which are so small that the large burner in the tankless basically
just fires up and stops, and the efficiency plummets - I equate it to
using a 747 to taxi down the block to the corner store and back. The
debate continues, but my understanding is that if the household uses a
tank of hot water or more a day, the standby losses from a storage
tank are less than the cycling losses of a tankless. I would recommend
a solar-compatible storage type water heater with a modulating boiler,
such as the Phoenix, or an air-to-air heat pump integrated with the
solar storage tank which comes from the solar supplier (almost all of
these tanks come equipped with an electric resistance element whether
you want it or not.) You might also find that you can offset the
backup solar thermal energy with PV, even if using electric
resistance, but gas or heat pump will make it about 3 times easier...

Graham Irwin
AIBD, CPBD, CGBP
Remodel Guidance
415-258-4501

Residential Design • Plans & Permits • Green Building • Period
Homes

[Dan Johnson]

Thanks for the feedback. Unfortunately I think to improve the system,
we need products that are not available. Agreed? (With the possible
exception of using the Phoenix gas water heater--I'll update the
diagram with this). My replies to Graham's points:

1) Gas is being offset at a rate of 1 kWh PV production = 3413 BTU of
gas consumption. This is the most conservative theoretical way to do
it, but I'll admit that you really can't offset burning natural gas.
And 1 kWh electricity run through a heat pump will make 7000 to 10,000
BTU of heat, so why not go all-electric?
A) Because PG&E is burning gas at the power plant to make electricity
in the first place.
B) I just searched for an hour for a suitably small, cheap, ducted
air-to-air heat pump and couldn't find one
C) What we really need is an air-to-water heat pump as backup for the
solar hot water (and hydronic space-heating downstream). How about a
pair of 7000 BTU/hr AirTap water heaters?
(http://www.airgenerate.com/products/specs.html) I cringe at the
installation gymnastics you'd need for these units, and the noise
they'd make. Otherwise you've got the Unico RC chiller, but it's
oversized (http://www.unicosystem.com/Portals/0/Pdf_Files/UniChillerRCBrochure113004.pdf)
and too expensive.

2) I believe potable water is permitted in a hydronic coil but not in
a radiant floor; the coil pump has to run for a minute every six hours
to keep the water fresh. A pump-cycler control will do this. The
alternative is a heat exchanger to separate the hydronic loop from the
potable circuit (then you need higher water temp and two pumps).

3) I agree the tankless have flaws, but they're the cheapest, most
efficient way to make heat from gas. We'd rather use the Phoenix,
which integrates a buffer tank for better performance, but it's more
expensive (http://www.htproducts.com/phoenix.html). We might end up
with the Phoenix just because it's a condensing boiler and needs only
a PVC vent, while a standard tankless like a Takagi will need a steel
flue with clearance to combustibles, so the total install may be
cheaper with the Phoenix...any opinions?

Thanks, --Dan

[Graham Irwin]

Dan,

A few other thoughts:

1) The device you are seeking is called an "exhaust air heat pump"
water heater or a "heat recovery water heater." These are available in
Europe, where they are sometimes installed as the last item in the
exhaust air stream to "squeeze" every last bit of energy out of the
conditioned exhaust air, as in this diagram (taken from http://www.passivhaustagung.de/Passive_House_E/compact_system_passive_house.htm)

[Graham Irwin]

Interesting concept with the Heat pump water heater in these homes (http://www.ashrae.org/docLib/20081021_smallbuildingapps.pdf
) The feed to the HPWH was switched between the kitchen refrigerator
coils and the conditioned crawlspace for cooling and heating seasons,
respectively.

Graham Irwin
AIBD, CPBD, CGBP
Remodel Guidance
415-258-4501

Residential Design • Plans & Permits • Green Building • Period
Homes

[Dan Johnson]

Thanks Graham. One comment that may be interesting for the group:
I believe the max airflow on the Recoupaerator is 210 CFM (I'll have
to check the spec sheet) so we arrived at a max heating load of 8500
BTU/hr using 210 CFM and a 110 deg-F supply air temperature. Now
we're designing an envelope that delivers a heating load of 8500 or
less. This is the reverse of the typical process: we're sizing the
envelope to meet the load instead of the mechanical equipment. I
believe this may be a better process.

I had some conversations today that made me consider the merits of
electric resistance backup hot water (like Graham suggests) and
electric baseboard heat. In this case, our heating load becomes
un-linked from the supply air flow (which can remain at a low 80 CFM
by ASHRAE 62.2 minimum ventilation air). Then we can go higher than
8500 BTU/hr, but we start paying penalties in our source energy
requirement and net zero goal.

> I am aware of a couple such units in the US:
>
> http://www.thermastor.com/Heat-Recovery-Water-Heaters/ which is used
> in commercial installations, so it may be oversized and/or unsuitable
> to the task, I haven't explored it much. Here is a report on them (http://oikos.com/esb/41/eahpstudy.html
> )
> http://www.saveenergymaine.com/exhaustair.html
>
> It may be that the airflow required for these units will far exceed
> that required by the Passive House, so these devices may be
> "oversized" for such an application.
>
> 2) I have heard that the Airtap heat pump water heaters are noisy, but
> have no direct knowledge. My understanding is that they are quite
> reasonably priced. If one were forego trying to duct it, and simply
> install one inside the conditioned space, you would cause cooling
> there, which would raise the heating load in Winter, but lower the
> cooling load in Summer - it might be worth exploring whether the
> balance was in your favor - my work so far in our climate suggests
> that Summer cooling is as much a concern as Winter heating. I believe
> they also have some facility for redirecting the cooled air to the
> exterior in Winter.
>
> 3) The potable water integrated with the heating system is, to my
> understanding, subject to whomever is inspecting your project - some
> jurisdictions allow it, others don't but I am no expert in the
> implementation/installation - there are others in the group who are...
>
> 4) Your airflow rate seems high to me @ 210 CFM. The Recouperator runs
> from 70-200 CFM, so you're asking for more than it's top output to
> deliver your peak heating load. The "magic" number for peak heating
> load with Passive House is 10W/m2 (~1W/ft2, 3.17Btu/hr.ft2) where the
> heating load can be delivered through the ventilation air. Is this
> where your shell design is taking you? It may be worth increasing the
> shell's efficiency to reduce the peak heating load, especially because
> of our milder climate and the fact that you're aiming for zero energy,
> which means that any savings you don't get through the shell you pay
> for with a larger PV system, and that's an expensive tradeoff. Passive
> House was designed to deliver the most cost-effective balance between
> efficiency and construction cost, but that is based upon European
> climate and does not assume net zero energy as the goal. If your peak
> heating load exceeds the capacity of the ventilation stream, you might
> forego trying to use that airstream at all and install radiators, etc.
> You might also consider a direct vent gas fireplace for the really
> cold times...
>
> 5) When coupled with some further efficiency analysis as above, you
> may find that the backup resistance element in the solar thermal tank
> isn't a huge load to offset with PV, and that the savings brought by
> eliminating the backup heater (the resistance element comes with most
> solar thermal systems "for free" anyway) can buy the extra PV panels.
>
> 6) Likewise, analyze the cost of larger PV system vs the cost of the
> Phoenix compared to the tankless and see where you come out.
>
> Interesting project!!!

>
> Graham Irwin
> AIBD, CPBD, CGBP
> Remodel Guidance
> 415-258-4501
>
> Residential Design • Plans & Permits • Green Building • Period
> Homes
>
>

> On Jan 21, 2009, at 10:51 PM, Dan Johnson wrote:
>
>>

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>
>
>

[George J. Nesbitt]

Dan Johnson wrote:

George, I'm curious about some of your comments (I haven't copied the group).
You said that Nabih's house is in the 12-15 kBTH range, though PHPP
would put it around 5 kBTH.  Can you elaborate on this?  I believe
12-15 kBTH for Nabih's house puts it beyond the 10 W/m2 heating load
"recommendation" from PHI.  To get 12 kBTH, you need 110 degF supply
air at about 280 CFM (70 degF room temp).  The Recoupaerator
literature says: max 210 CFM.  How do you get the remaining 70 CFM? A
booster in-line fan?  You have to start up-sizing all your ductwork?
And why does PHPP say you only need 5 kBTH?

Also could you explain why you had to increase your CFM on the Gerstel
house so the smallest registers would work?

Thanks for the insight.
--Dan

  

Thanks Dan, are you sure you are an Architect?

    1. Load calculations; ASHRAE or Manual J load calculations for heating do not include internal loads, and I have heard the safety factor is as much a 60%! The PHPP does include internal loads and probably does not have the same large safety factor. So that would explain the large differences.

    2. The 10 W/m2 recommended heating load is based on...

    3. Yes the ERV only delivers 210 cfm, and your calculation is correct (Btu = cfm x 1.08 x delta T). So if you needed more heat you can increase the cfm, or the delta T! And we have not converted Nabih's house from electric baseboard to hot water yet. I am waiting for answers to the PHPP.

    4. Duct design for architects; the more air, the longer the ducts, the more fittings and direction changes, the larger the ducts need to be (please design space for us to install them!). The cfm and velocity of the air at the register is related to the size and style of register you use, and how far it "throws" air into the room and mixes the air, and how much noise it makes, and how comfortable it is. My cfm's were too low for the smallest grills for Gerstel's house, that why I increased it.

On Mon, Jan 12, 2009 at 8:17 PM, George J. Nesbitt
<geo...@houseisasystem.com> wrote:
  

[George J. Nesbitt]

Mechanical equipment should be designed to the envelope, but most of the time is not. Design the envelope to the mechanical equipment works too, and should be done, but also is not done most of the time either. It's a chicken and egg situation, which comes first, when in reality they both have to exist.

Design with the mechanical systems in mind, design the mechanicals based on the design, etc....

Electrical backup to solar hot water makes some sense, but instantaneous makes more, why heat what you don't need?

While with small loads you may be able to heat with electric baseboards, I would discourage it. You take a hit on CA T24 as well as with the PHPP. While from a site energy standpoint 100% efficient electric is more efficient than any gas heat, you take a big hit based on source energy. If you go electric, you have to think about heat pumps, and we can add that into the ventilation system too.


Dan Johnson wrote:

....
              

[Graham Irwin]

George,

What he is talking about is totally ass-backwards from a PH standpoint. You design the shell to minimize the mechanical system and the goal is heating through the ventilation stream, i.e. 10 W/m2 max heat load.

Graham Irwin

AIBD, CPBD, CGBP

Remodel Guidance

415-258-4501

Residential Design  •  Plans & Permits  •  Green Building  •  Period Homes

 

[George J. Nesbitt]

I think how we do most things as standard practice are "ass backwards".

I think that designing the shell to be efficient enough to be able to supply the heat through the ventilation system is a great design goal, and does not contradict you second sentence!

Graham Irwin wrote:

.....
              

[Craig]

Are you multi tasking?

[Graham Irwin]

I would prefer that PH practice not join standard practice in that regard. The intent and the goal is to maximize feasibility through efficiency improvements to the point of mechanical equipment savings. As is said here: http://www.passivhaustagung.de/Passive_House_E/compact_system_passive_house.htm

"...in a passive house, the peak heat load requirement is extraordinary low. Indeed, it will be so low that these 10 W/m² available from a fresh air supply will be sufficient (that in fact is the defining condition for a passive house)."

The PH standard does not require this cost savings, but much of the development of the standard, and the concept itself, was based upon this economic "sweet spot." I am not sure how difficult it is to design a building which meets the PH standard in this climate yet vastly exceeds the peak heating load, I have not tried.

My apologies to Dan, et al, for my harsh language previously, it's been a long day (week, month, etc.)

Graham Irwin

AIBD, CPBD, CGBP

Remodel Guidance

415-258-4501

Residential Design  •  Plans & Permits  •  Green Building  •  Period Homes