HRV/ERVs in the Northwest?

[Win Swafford]

If you haven't already seen John Semmelhack's provocative ventilation study check it out.  It is also the subject of Martin Holladay's current blog.  

How does this pertain to us in the Marine 4C Northwest?  The low-income PH pilot we are working on in Eugene is unlikely to be replicated in part because of the cost of the ventilation system.  It would be nice for PH design to be intelligent design (pardon the phrase).  I certainly appreciate the impetus this study places on manufacturers to keep systems costs inline with savings to be recouped.  

Way to stir it up John!

[John Semmelhack]

Thanks, Win. For those who read the study and/or blog and who are also working on townhouses and/or multi-family housing in the NW, please check out my comment #34:

Follow-up with Mike Eliason regarding multi-family buildings...
by John Semmelhack 

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In climates where clients are willing to forgo cooling systems AND the winter design temperatures are relatively mild (I'm thinking Portland and Seattle, for instance) the peak heat load in multi-family buildings with HRV/ERV systems can be low enough that ALL of the space heating energy can be delivered via the ventilation air (without increasing the ventilation rate!). This, of course, is the classic PH space heating strategy - high performance HRV/ERV, high performance domestic water heater tank, a small pump and a water-to-air heat exchanger to move heat as needed from the tank to the ventilation airstream. Maybe $8,000-10,000 installed for everything (ventilation, space heat and DHW)? These situations are where the economics start to swing back in favor of HRV/ERV, in my opinion.

On the other hand, this concept is much more difficult to achieve for buildings/clients that require space cooling. 

____________________________________
John Semmelhack
Think Little - Small Solutions for a Big World

semme...@think-little.com
(434) 409-3970 - tel
www.think-little.com

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[Bronwyn Barry]

John,  

Thanks so much for the interesting study.  It certainly has me re-thinking ventilation and possible alternate solutions to drive down cost without sacrificing performance or good IAQ.  

The only thing we can all guarantee at this point is change.  In this regard, I had an interesting conversation today with some folks from NY.  Apparently there will be an option available in the near future for a very simple E/HRV unit similar to the Lunos wall-mounted, ductless unit.  It installs in the window, much like a conventional window A/C unit.  I have no idea what the pricing on this unit will be, but if it does actually perform at the 90% efficient recovery rate that has been claimed, the economics of separate E/HRV's combined with mini-split/heat pumps for cooling and heating will change again. I've also heard talk of another locally made 'compact unit' that will again simplify our mechanical systems, or at least give us more options.  I look forward to learning how these changes will affect the results of your study.

There really isn't a dull moment in the PH world, is there?!

Cheers,

Bronwyn

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Bronwyn Barry, Assoc. AIA

Certified Passive House Consultant
Director - One Sky Homes

m: 415.819.7978

t: @passivehouseBB and @oneskyhomes

http://www.oneskyhomes.com/video/hair-dryer-home

     

www.oneskyhomes.com

[Hayden Robinson]

Thanks for your work John. And for including SEA and PDX in your investigation.  I enjoyed reading the study, and the GBA discussion around it.

 

Hayden Robinson AIA, Passivhausdesigner

hayden robinson architect

206.691.3445

www.HaydenRobinson.com

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[Hayden Robinson]

John Straube made an interesting point in his webinar earlier this month. If I understood him correctly, he indicated that the 130F limit on supply air was an artificial one because pyrolisis could be minimized through filtration rather than temperature control. I wonder if he doesn't have a point, and if maybe peak heating couldn't be handled with the ventilation system in a larger range of projects. Or, if in places like Seattle, we couldn't get by with 130F supply air, and a couple of electric-resistance heaters for those couple of 20F nights we get each year (during hours when everyone is warm in bed anyway).

 

Hayden Robinson AIA, Passivhausdesigner

hayden robinson architect

206.691.3445

www.HaydenRobinson.com

 

From: Passive...@googlegroups.com [mailto:Passive...@googlegroups.com] On Behalf Of Bronwyn Barry
Sent: Monday, December 17, 2012 7:01 PM
To: Passive...@googlegroups.com
Subject: Re: HRV/ERVs in the Northwest?

 

John,  

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[John Semmelhack]

Thanks, Hayden & Bronwyn. 

Regarding 130F supply air (PHPP actually uses something slightly lower - 125.6F!) - I caught the same reference during John Straube's presentation. It would be interesting to explore further. For instance, has he done this before? What kind of filter? How hot has he gone? 

One other limiting factor is the tank temperature. For instance, even if filtering took care of all of the dust, in order to get 140F supply air the tank temperature would probably have to be 150F or more, since there will be a small heat loss between the tank and the water-to-air coil and the water-to-air coil will not transfer 100% of the delta-T between the water and supply air.  

Hayden - I'm pretty sure Dan Whitmore is employing the strategy you describe at his PH. I think he's covering ~80% of his peak heating load by heating the ventilation supply air (using a high efficiency natural gas DHW tank as the heat source), and the other 20% of peak load via electric baseboard. Dan - care to chime in? I think this is good strategy….not sure how easy it is to "lock out" the electric heat until it's actually needed. 

-John

 

____________________________________
John Semmelhack
Think Little - Small Solutions for a Big World

semme...@think-little.com
(434) 409-3970 - tel
www.think-little.com

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[Dan Whitmore]

Hi All -

Yes, John, I did install such a system in the Courtland Place PH. It's working fairly well, the only issues are due to the occupants not being too interested in altering their behavior patterns. The place is rented and the family who lives in the main part insists on opening the windows for 15-60 minutes each morning to 'air out the house'. No level of Mechanical ventilation discussion has successfully convinced them that this is being accomplished via the whole-building system.

The end result is the water-to-air heating coil in the ventilation system does work more to try maintain the temperature. When open windows are forgotten for hours a day the load does take a while to meet. That said, it still hasn't topped ~$12/month for gas associated with space conditioning. (Gas bill is ~$25 in non-heating months for 2 kitchens and all DHW, $37 for last January) but there have been some complaints about the house not being able to heat up quickly.

Of the electric space heaters in the building, only the one in the main house is occasionally used. The one in the apartment hasn't been turned on for 2 years, since the occupants who mainly live in the tropics/SE Asia returned  and a Pac NW'er moved in. The original idea for control was to have a thermostat on the elec heaters which would be set to 66 or 67 deg F so it would only cycle on when the main system was unable to keep up. A more integrated option would have been to install a relay so the elec resistance would only come on if the pump for the Water-to-Air coil was also on. However cost considerations and the decision to have the building be rented out tipped the hand to simply having a timer on the 1000 watt wall heater. If the occupants want add'l heat they need to turn a dial. Glad I went this way considering the occupant behavior.

Cheers - Dan