Comments on: Passive House Appeals to Home Energy Raters

By: Ken Riead

Ken Riead — Tue, 14 Aug 2012 00:57:31 +0000

I thought there might be
I thought there might be interest in a Passivhaus built on a budget. Here’s some links:

http://www.treehugger.com/modular-design/prefab-platinum-prescott-passive-house-built-on-a-budget.html 

http://studio804.com/projects/prescott/project%20overview/prescott_overview_01.htm 

Great article, as always!

By: Ultimate Air

Ultimate Air — Tue, 06 Mar 2012 03:35:32 +0000

Having a complete passive
Having a complete passive house means having a good air filtration system. At UltimateAir we have developed an award winning air filtration system that is complete with an energy recovery system as well as heating and cooling options. Our product has been termed “green” not only by engineers and professionals but has been recommended for health related issues such as asthma and allergies as well as respiration issues. Even without these, doctors, builders, and buyers are suggesting this product for all houses, offices and schools and most of all to complete the requirements to be called a passive house. Check out our product called the RecoupAerator at http://www.ultimateair.com 
or if you are a contractor or a design professional, or visit http://www.ultimateair.com/commercial-air-purifier/learn-more/ 
for more information

Thank you!

By: David Butler

David Butler — Mon, 05 Mar 2012 10:21:08 +0000

sorry, I mean Katrin
sorry, I mean Katrin

By: David Butler

David Butler — Mon, 05 Mar 2012 10:20:12 +0000

Hi John, just to clarify, the
Hi John, just to clarify, the builder dealt directly with Kristin on this project. To my knowledge, the recommendations came from her. Ryan worked up the climate data, and Ian did some additional modeling on the slab insulation question, but PHPP drove the recommendations. The walls were already over the top (9.25 inch TJI "stud" cavities filled with cellulose), and the window specs were 0.22/0.15. That, plus 0.6 ACH50 is just nuts for this climate (Sierra Vista).

The local microclimate is about 5 to 10 degrees cooler than Tucson due to higher elevation. Like Tucson, we have long periods of cloudless weather in winter, with relatively mild afternoons. This means that homes optimized for passive solar gain can offset much of the annual heating load with solar gain. I don' believe PHPP does a good job predicting that. No software does, really. Also, the nearest TMY dataset is Douglas, AZ, which generally has colder winters and hotter summers, even though we're at a higher elevation. Go figure. I think that contributed to the over-predictions of heating and cooling energy.

My own home, which was built in 2005 by a production builder, only requires ~900 kWh/yr for heat (I have a sub-meter for my 15 SEER heat pump). The house has 2,550 sf. Walls are 2x6,16oc with R19 batts and R4 EPS continuous. Attic has R30 cellulose. Ducts are tight, but in the attic. Glass is not low-e, although vinyl sliders are tight. There's no slab edge insulation. The house tested out at about 3 ACH50 and ducts are tight. No modeling software comes close to predicting my annual heat load.

One final note... the builder is totally committed to getting PH certification (as well as LEED Platinum). He saw this as a challenge, which it was. We all learned something and that's always a good thing!

By: John Semmelhack

John Semmelhack — Mon, 05 Mar 2012 08:26:58 +0000

For David Butler,
For David Butler,

Regarding the Passive House in Arizona - I don't know anything about the project. I don't disagree with any of your comments, other than to suggest that the designer or consultant made certain recommendations...not "Passive House" or the PHPP modeling software.

I have a digital "test hut" (20x40x2 stories tall) that I paired up with the Tuscon climate data in the PHPP modeling tool. With just 30 minutes into it (never having previously worked on a house in the SW), I was able to get the house to meet the PH annual sensible cooling and heating requirements with the following rough performance specs paired with excellent summer shading and good passive night ventilation/cooling:

Slab - uninsulated
Walls - R-20
Attic/ceiling - R-40
Windows - U=0.30, SHGC = 0.23
Ventilation - HRV with mediocre heat recovery (60%)

By: David Butler

David Butler — Sat, 03 Mar 2012 01:02:37 +0000

Chris wrote:
Chris wrote:
> These things can sit behind a 20x40 return filter grill real nice.

That's exactly what my design called for. Makes the filter almost disappear.

By: Chris Cadwell

Chris Cadwell — Sat, 03 Mar 2012 00:54:41 +0000
Good points David on the
Good points David on the Energy Recovery Ventilation and the slab insulation. That would not work in the SW as well. I have also heard that the home would possibly get too hot in the winter and may need to be conditioned in this type of climate.

I am also starting to favor the simple ducted mini-splits with hard pipe supplies and un-ducted return. Was just looking at these yesterday. These things can sit behind a 20x40 return filter grill real nice.

By: David Butler

David Butler — Sat, 03 Mar 2012 00:40:49 +0000
I think PH is great for cold
I think PH is great for cold climates, especially areas without access to natural gas. But in warm climates, high levels of insulation and atomic air sealing are hardly cost-justified.

I recently worked on a local Passive House project here in SE Arizona. Aside from obvious overkill on envelope u-factor, here are my observations:

PH recommended a very expensive, super high efficiency ERV, hardly an appropriate choice for our mild, dry climate.

PH recommended sub-slab insulation. The cost benefit of sub-slab insulation is questionable in hot climates, where the small winter benefit is traded off against loss of the passive cooling benefit of full ground contact in summer.

PH only assumed 1400 btu/hr internal design load for appliances and six persons.

Although my total heating and cooling design loads weren't significantly different than PH's, I was not comfortable recommending a single wall mount mini-split to condition the home. In particular, since solar gain dominated the cooling loads, it's important to get the air to where it's needed in hot climates. I recommended a small ducted mini-split with unducted return and super low-friction supply side.

By: Paul Price

Paul Price — Sat, 03 Mar 2012 00:34:54 +0000
In general Passive House is
In general Passive House is pushing us to think differently and that's a very good thing.

I have done the two day PHPP (the Passive House software) course so I know enough to say PHPP is a very good tool, even if you are not building to Passive standards, in assessing the effects of varying insulation/glazing amounts in different parts of a design .

However, as our instructor pointed out, it is quite possible to build a huge, Passive house with floor to ceiling glass facing north (to get the view over that way) as long as you throw enough insulation elsewhere and get the solar gain/shading right.

We live in a small, ninety year old, far-from Passive home but it has energy consumption of a very costly to build, 6000 square foot Passive mansion. In a world where we need to be concerned about energy consumption, energy security and GHG emissions a standard that does not penalise house size and total energy consumption still has a way to go.

By: Allison Bailes

Allison Bailes — Fri, 02 Mar 2012 22:09:44 +0000
Chris C.:
Chris C.: I think it's a great concept, too.

John S.: Thanks for clarifying. I've revised the article to correct the part about solar and internal gains. And yes, I'd love to learn more about the VA and NC Passive House projects you mentioned.