This green home will heat itself

July 24, 2009 4:00 AM PDT
This green home will heat itself
by Martin LaMonica

For all the complex solutions proposed to lower building energy use, Simon Hare has a project to demonstrate the power of simplicity in green buildings.

The design-builder earlier this year began reconstructing an 1850 cottage in Boston's historic Roxbury Crossing neighborhood to be so energy efficient that it wouldn't need any mechanical heating.

His work is inspired by the Passive House standard, which is based on a set of principles for building energy-efficient homes that took root in Germany in the late 1980s. But Hare has another goal: to show that net-zero, or very low, energy homes are within reach of everyday building professionals.

A green home grows in Boston.

(Credit: Martin LaMonica/CNET)
"The Passive House approach is very techie, which I think is its Achilles Heel--it appeals to geeks but not the layman, the lay builder," Hare said standing in the half-finished home last month. "We can prove we can do this without hiring consultants and using software to do the energy modeling. We'll just use precedent and established rules of thumb."

The Pratt House project is an example of a burgeoning movement in the building industry. With the growing concern over the environment and energy, builders and architects are devising ways to dramatically cut the energy use in people's homes, for both new construction and retrofits. In the U.S., all buildings represent about half of greenhouse gas emissions, according to the U.S. Green Building Council.

A more high-tech approach to super-efficient homes could be control systems that optimize a home's mechanical systems, such as heating and lighting, or demand-response appliances that can take advantage of off-peak electricity prices.

Photos: A Passive House in the making

By contrast, many builders like Hare are starting from the ground up by taking steps to lower the energy load that a home needs to operate. In practice, that boils down to constructing an air-tight building with lots of insulation and energy-efficient appliances.

When you add distributed energy, such as solar panels for hot water and electricity, to a well-sealed and insulated home, homeowners can dramatically cut utility bills and potentially get to net-zero energy use. Following the Passive House guidelines, for example, can lower energy use by 60 percent to 70 percent and drop the heating load by 90 percent.

Trickier than it looks
Hare's project in Roxbury, which happens to be his family's house, started out as a retrofit. The building, which once was a workshop for a 19th-century gunsmith, had been abandoned for 20 years before he acquired it. After construction began, the crew at his firm, Placetailor, discovered serious structural problems and the cottage was torn down and rebuilt with the exact same dimensions.

Since it's a new construction, they were able to take particular care with the air sealing. The frame of the home is built using structural insulated panels, which are 12-inch layers of foam insulation sandwiched between two sheets of plywood.

A layer of one-inch rigid insulating foam on the exterior walls brings the r-value (a measure of insulation) to 50, many times more than a typical home. The joints between the wall building blocks and the floor were taped or sprayed with foam to make the building more air tight.

Hare borrowed a fog machine from a local DJ during two blower door tests to see where air was escaping from the building, viewing it both from the outside and from the basement. Many tweaks made the house very tight with 0.6 air changes an hour, which for a building that size translates to 60 cubic feet per minute.

In an unusual twist, the floor is made of concrete and the interior walls, too, will be made of similar material. That material acts as a "thermal mass," able to retain heat in the winter or absorb heat from the air in the summer to maintain a comfortable climate, Hare explained. By adding solar panels, the Pratt House could easily be a net zero-energy home, he said.

Although it's rarely done, builders have been converting existing homes into these sorts of superinsulated buildings for decades. One way is to put foam board insulation on a home's exterior walls and roof while another option is to spray insulating foam onto the exterior and add shingles on top of that layer.

Adding that exterior layer of insulation is expensive upfront and, in practice, tricky when dealing with windows, doors, and drainage considerations. But a bigger barrier to better-sealed homes is simply inertia given that most contractors don't pay attention to how air flows in buildings.

"The basics are simple--a lot of insulation, a very tight building, and efficient appliance," said Hare. "But a regular construction crew would just put up a wall quickly and never stop to think about sealing cracks and leaving places where you want air to go through."

Homes that are extremely air tight need a heat-recovery ventilator which brings in outside air mechanically, while heating the air as it enters.

Miles per gallon for homes
In parallel to the push for more efficient homes, there are more calls for benchmarks and performance standards. Right now, builders and homeowners are largely "flying blind" when it comes to making efficiency improvements, according to Paul Eldrenkamp, of design and build firm Byggmeister, who is the first Passive House-certified consultant in New England.

The original structure, an 1850 gunsmith's workshop that had been abandoned.

(Credit: Placetailor)At the Pratt House, the approach is to build first and analyze later. Hare went that route because he's concerned that exhaustive up-front analysis, which might involve modeling software and complex spreadsheets, is too intimidating to most builders.

"People in this whole movement say that there needs to be standards but they are so far removed from established building practices--it's just another barrier in adopting these things," he said. "Passive House is a very strict standard. You could fall short by some fraction but still have an excellent building."

The target is to have the Pratt House nearly complete by October, which is when the big test for his experiment begins. In the winter, the goal is to maintain a temperature between 63 and 65 during the winter without supplemental heat. So far, in the summer, the home has stayed cooler than the outdoors, thanks in part to the concrete floor which absorbs heat and makes it feel cooler.

This sort of home is clearly not for everyone. It's very small at 750 square feet and the people inside will need to manage the temperature more actively than simply setting the thermostat. For example, to gain heat in the winter, they will need to open the south-facing shades during the day and close them at night to retain heat. In the summer, too, they open the windows at night to cool off the thermal mass of the building.

On the other hand, the materials involved are cheap or recycled. "You don't need fancy expensive windows from Germany," said Hare. And many of the construction techniques can be applied elsewhere. Placetailor, in fact, is involved in another local project called the JP Green House which aims to convert a 100-year-old home to be carbon neutral.

"We had this feeling that if (efficient homes) are going to be widespread, you should be able to do it with common sense," Hare said. "Otherwise, it's just a geeky pursuit or it's rocket science when most people just want a house."
Martin LaMonica is a senior writer for CNET's Green Tech blog. He started at CNET News in 2002, covering IT and Web development. Before that, he was executive editor at IT publication InfoWorld. E-mail Martin.
Topics: In the home, Green buildingsTags: green buildings,

Recent posts from Green Tech
Greening the home--from low effort to high tech
MIT spin-off stores sun's energy to power the world
Clean-energy wonks to Washington: Get a clue
Volvo promises a plug-in
Battery maker A123 Systems charged from IPO
Even with great tech, no easy answers on energy
Why all the requests for paperless billing lately?
GE: Solar business is our 'next wind' Related
Students build solar home that's no gimmick
IBM data center gets deep energy retrofit
Clean-energy wonks to Washington: Get a clue
Pittsburgh gets its own Green Monster
Silver Spring buys Greenbox's Web energy software
New school year brings 'Green IT' college degree
Jet-engine inspired FloDesign boosts wind turbine output
Carnegie Mellon goes green with Gates-Hillman complex

(28 Comments) prev 1 next by greenireland July 24, 2009 4:51 AM PDT
Great idea, we are also working on Air Tightness testing and can say that it does matter a lot. Unfortunately under the current Irish building regs the allowed Air Permeability rate can't exceed 10m3/hr/m2 @50Pa which is way too high for an adequately built home. Fair play to you guys for starting to build right, showing everybody that it can be done and doesn't have to cost a fortune.
Any chance we can link our blog to your article?
Reply to this comment by mlamonica July 24, 2009 5:19 AM PDT
Sure, feel free to link to (but not reproduce entirely) .Here's the URL :http://news.cnet.com/8301-11128_3-10293753-54.html?tag=mncol;title Here's the URL of the photo gallery : http://news.cnet.com/2300-11128_3-10001256-1.html?tag=mncol;txt
by dbargen July 24, 2009 5:20 AM PDT
Hey, Martin,
Can we get a price tag on that home? Maybe without the demo costs, just to make it fair.

One item I'm surprised wasn't addressed was heating and cooling systems, and what controls vapor between all of those layers of insulating material. The way they talk about "concrete holding in the heat," I'm surprised there wasn't note of radiant heat systems put into the slab as it was poured.

One of these days, we'll actually see a side-by-side comparison of construction costs to let us see if it's *really* worth it.
Reply to this comment by pixelpusher220 July 24, 2009 8:41 AM PDT
Comparing 'construction costs' isn't a fair comparison. The false comparison is that these green builds will *ever* be cheaper than a normal build....*today*.
.
The real comparison would require the accurate pricing of the resources and detrimental effects of those resources used for power, heating and cooling. Then you'd know the true cost of a regular build and a green build. Over time the green build would be significantly cheaper.
.
The problem is that *today* we don't price in all the costs associated with energy production; we only factor in fuel and infrastructure costs. The costs associated with releasing massive amounts of greenhouse gases and other pollutants isn't factored in. That's where the real savings of a green build are found.
.
Once you move to renewable fuel sources, green gets even better as your 'fuel' costs start to disappear as well.
.
It's the same with cars. No electric vehicle will ever be cheaper than a gasoline car *today* when it comes to fuel and power density. Over time, as gasoline prices rise electrics will stay relatively constant and/or drop a bit with efficiency. That's when electrics come into their own. Unfortunately, the environment may not wait for that to happen.
by mlamonica July 24, 2009 9:16 AM PDT
This house isn't going on the market since the builder is the owner. He doesn't have a very accurate number on cost but said it's in the range of $240/ square foot for construction. They plan on publishing that info when the complete the project in the fall, but the goal all along was to keep it relatively inexpensive.

There was another article on superinsulated homes. See here. http://news.cnet.com/8301-11128_3-10123367-54.html?tag=mncol;txt
There is a significant upfront cost to doing that sort of deep energy retrofit and there are different ways to calculate your payback (see the Byggmeister link in article). But clearly your ongoing utility/operating costs will be lower.
by kyoung5446 July 24, 2009 10:00 AM PDT
As an employee of Placetailor, the 'project manager' for this project, and member of the construction crew, I will try to shed some light on your questions.

The price tag is a little tricky to figure out because the company was being established while this project was being built. Company startup costs and construction costs were not always separated. Our estimates for construction are between 120k and 150k, certainly a steal for Boston. Costs were kept low by having a small (2 man+ temp help when needed) construction crew, and many late nights put in by Simon, the homeowner.

Our goal for this project was to achieve the Passive House standard, which requires a very low annual heating and energy load (? 15 kWh/m2/year for heat, ? 120 kWh/m2/year for primary energy). So low in fact, that having traditional heating (including radiant) and cooling systems pushes the house over these limits and is not an option. Therefore, the primary source of heat for the house is the sun. By using very dense masonry materials on the interior (concrete floors, stucco walls, bricks within interior partitions) the house absorbs and stores the heat from the sun during the day, and slowly dissipates it into the space throughout the night. The use of dense materials to capture energy is called 'thermal mass' and is one technique among others that we employed to achieve our goal of no heating or cooling systems.
by kyoung5446 July 24, 2009 10:03 AM PDT
That should be (LESS THAN 15 kWh/m2/year for heat, and LESS THAN 120 kWh/m2/year for primary energy)
by Phil in MN July 24, 2009 12:23 PM PDT
Go to: http://www.passivehouse.us/passiveHouse/PHIUSHome.html
In most cases these homes can be heated with a hair dryer so ther is no value in very expensive hitech heating plants. The money goes into the envelope vs. the hi tech equipment.
by ssanchex July 24, 2009 6:10 AM PDT
Every time I see or read about these "green" home projects I get really excited at the prospect of being able to take real case examples to my architect for my home's renovation. I was particularly excited by the retrofit of a 19th century home, given my home is also from the same period. Then comes the inevitable let down from many of these projects; a concrete thermal mass. Concrete's use of Portland Cement means that is has a massive up front carbon output. So whilst the house may be cheap to run and carbon neutral on an on going basis, many of these homes will take up to 20 years to repay the carbon released in the manufacture of the concrete they use. Using large amounts of concrete is one of the least "green" things you can do when building or renovating your home.

Does anyone know of anyone using lime-crete (a Portland cement free concrete) as a thermal mass; does it have the right thermal properties?
Reply to this comment by Orengeman July 24, 2009 6:56 AM PDT
Where are the windows on this house? How dark and dingy is it going to be on the inside? The original structure had 3 windows on the street side - 1 up, 2 down, but the new house has only 1 on each floor, plus no windows on the long side and a small window on the single-story portion in the rear. How many people out there want to live in a small dark cave?
Reply to this comment by mlamonica July 24, 2009 6:59 AM PDT
There are big windows/ glass doors on the south side, placed there to let light and heat in. See the photo gallery: This picture gives you an idea of the back: http://news.cnet.com/2300-11128_3-10001256-6.html?tag=mncol
by iamarcin July 24, 2009 7:00 AM PDT
This building has stood for 150 years.
Id say that the improvements over its life time would have at least paid for themselves.
Reply to this comment by findmorefollowers July 27, 2009 5:23 PM PDT
The article said they had to tear the original building down due to structural faults... and a replica was built in its place.

[CNET editors' note: Spam deleted]
by whobob July 24, 2009 7:05 AM PDT
My father had his store built with a foam block building system. Found that even in winter where tempuratures are routinely below -20C (about -4F) that the heat generated from coolers in the store pretty much kept it heated. Of course in the summer he had to air condition a lot more than normal so maybe in his case the overall change in energy use was not that much.

A house of course would not have so much heat producing equipment in it. Super insulation can make a lot of sense in that case.
Reply to this comment by pjcamp July 24, 2009 8:19 AM PDT
I hate to point this out, but if he tore it down and rebuilt it, that doesn't count as a retrofit.
Reply to this comment by MischaMAC July 24, 2009 9:28 AM PDT
I want one!
Reply to this comment by danieliusC July 24, 2009 9:35 AM PDT
Another air tight home. When the HVAC system is not blowing air- the air is bad- very bad. Why is that good? Why go to such extremes? Its not necessary or very smart. High tech this- high tech high cost that. You can build a better, heathier, more pleasant to live in home for lots less money - I have. I live in it. With few exceptions there is no tech younger than 100 years. This is not a home- its a prison. You want to be a slave to the bank? or a slave to your high tech junk? My home has some similar characteristics- but I kept it real simple - my interior walls are brick- used brick- how is that for green. there is not a single fan or air moving device other than what gravity provides and some clever use of basic physics. No boxes of fans and heat exchangers taking up space and electricity. If the power goes down in this house it becomes toxic. I would not want to live in this little experiment- 10 bucks says they guys partner leaves him within a year of moving in.
Reply to this comment by ArtInvent July 24, 2009 9:39 AM PDT
You touched briefly on the air exchange systems pioneered in Germany. This is extraordinarily important since a super airtight building will need a constant supply of fresh air, and that system needs to somehow conserve the temperature inside the building. Without a very efficient heat exchanger the whole concept wouldn't be possible. A related consideration is making sure all spaces stay dry to avoid fungus which has been a big problem in earlier sealed and super-insulated homes. Again the key is ventilation without losing temperature.

Living in So. Cal. (or almost anywhere in CA for that matter) most homes still have heaters and AC. That's tens of millions of unnecessary units sucking power. We could probably skimp a bit, not be quite so stringent on insulation R values and airtightness, and still manage to build homes that need zero added heat or cooling. I am slowly converting all my windows to dual panes, but even with modest improvements to insulation and smarter systems, it can take very little energy in this part of the country to maintain a comfortable temperature.

In the summer, it's kind of shocking how well a substantial whole house fan can cool the house at night.. With good insulation, it's not hard to conserve that temperature throughout the day and eliminate AC. Yet almost no homes have a good system to really push the nice cool air outside into the home at night and push the warm air out. It really takes fans pushing air inside in certain locations, and out through the attic in other locations.

It's time to stop just throwing up marginally insulated buildings and bolting on the heater and AC units. Thanks for this article and hope to see more like it.
Reply to this comment by MD_Willington July 24, 2009 9:51 AM PDT
A lot of existing structures can be retrofitted in a similar way with a Larson Truss system, the system was invented in Canada, it is a pretty simple retrofit. Or you can build it that way to begin with.

Of course the SIPs do a great job too, SIPs are hardly new technology however...

http://www.builditsolar.com/Projects/SolarHomes/LarsenTruss/LarsenTruss.htm
Reply to this comment by ecotopian--2008 July 24, 2009 10:51 AM PDT
IMHO - Air Tight is not the way to go. It can create very unhealthy conditions. I once worked on a "Double-envelope" house which had both inner & outer walls with air circulating in between. Extremely expensive to build, by the way. On the south side, this air gap opened into a solarium which created plenty of warm air that circulated through the entire envelope. Worked great, but only for one purpose. The air in the house smelled bad, the wife was sick & the baby miserable. I support Green Design 100%, but solutions that solve one problem by creating another will not fly. Fred Stitt, Green Design expert at SFIA, the San Francisco Institute of Architecture, says a properly designed passive home does not need tight seals and hyperinsulation.
Reply to this comment by Phil in MN July 24, 2009 12:28 PM PDT
In our cold climate (MN) we have data on air leakage of about 8,000 houses built before 1960. 30% are in need of mechanical ventilation, 30% are ok in ventilation and only 30% are over ventilated. Houses can be much tighter than you think.
next issue: distribution of fresh air. Can you predict that air leakage will be uniform through the home (nope!)
Mechanical ventilation can assure quantity and quality if done properly.
by Phil in MN July 24, 2009 12:32 PM PDT
forgot one or two points: point 1 with energy recovery you can reduce energy use and control comfort
2- energy recovery can reduce ac loads in humid environments by rejecting water vapor to the outside.

It really comes down to not being able to make a house tight enough. (here is a wild irony! We have been building specialized buildings - Hog Confinement buildings like this for almost 40 years now! - about time we treat people as well as pigs!)
Reply to this comment by aazippo1 July 24, 2009 1:43 PM PDT
How about a green home that will COOL itself!!!

RT
www.privacy-tools.tk
Reply to this comment by mkernagis July 25, 2009 11:43 AM PDT
Hello Mr. LaMonica,

Having recently read "This Green Home Will Heat Itself," I was gratified to see an examination of super-insulated and very efficient buildings. But I find myself disappointed and frustrated at the portrayal of Passive House. I am a co-founder of the Passive House Institute US, and feel a need to counter such misinformation as that offered by Simon Hare. I contacted Mr. Hare several months ago when I saw he was calling this project a Passive House. Though an interesting project, originally intended to be a retrofit and also making use of recycled product, his building was definitely not designed or built to the Passive House standard; and he clearly resented that I'd called him out and cut into his attempt to capitalize on our good name for his marketing purposes. That you've portrayed such a one-sided and negative view of what we're up to seems to me to be poor reporting...on a topic that deserves very good reporting.
Contrary to Mr. Hare's assessment, PH does appeal to the lay builder. I myself came to it from a very conventional building background, as have about a quarter of our consultants. Many builders are ready to move beyond current practices and apply themselves to a new and accessible level of craftsmanship, establishing an advantage for themselves in the process. As an aside: I recently spoke with a staff member from Mr. Hare's own Placetailor, who was a student in our New York Passive House Consultant training program last week. He told me that their building achieved the airtightness Mr. Hare claims only after they had employed such "tweaks" as taping off their leaky double-hung windows - hardly a solution with the widespread appeal that Mr. Hare claims to favor.
We are strong supporters of analyzing a building to see that it performs as claimed; but also of developing best building practices to assure that it will be comfortable, safe and durable, and that it won't melt or mold from moisture-related issues. That analysis and development is precisely what the Passivhaus Institut has been doing, on a broad scale, for over a decade (To wit: http://www.passivehouse.com/07_eng/news/CEPHEUS_final_short.pdf ). Mr Hare is correct that the Passive House standard is a very strict one. It is intended to be. He is also correct to say that one could come up short of that standard and still have an excellent building. But excellent tight and super-insulated buildings also require design and construction care that goes beyond the norm, and that can vary dramatically depending on climate. It's not rocket science, but neither is it a conventional "rule of thumb". Nobody's trying to make it difficult or inaccessible. To the contrary...Passive House energy modeling software helps a designer to accurately assess economical energy design decisions for very low-energy buildings - and also, where needed, to install appropriate space conditioning systems.
PH is not simply a geeky pursuit. It is an applied building science. It is a profound and proven energy efficiency standard now being widely applied in tens of thousands of units in Europe. It is now code standard for new construction in many states and major municipalities there, who apparently aren't too inconvenienced by subtleties of building science. There is also a rapidly growing community of practitioners here in the US who are, unlike Mr. Hare, neither exhausted nor intimidated at the prospect of a little upfront analysis and consideration in order to effectively and affordably address our climate, energy and building science issues.

Mike Kernagis
Passive House Institute US

Reply to this comment by jpgreenhouse July 28, 2009 10:17 AM PDT

Mike, I think the article by Martin LaMonica is well written and insightful and the response posts raise pertinent questions to which passivhaus advocates have persuasive responses, many offered above.

Your comments are somewhat jarring in this otherwise interesting and collegial conversation, however, and as co-founder of the Jamaica Plain Green House and Placetailor's first client, I don't think you have fairly characterized Simon Hare's views.

The two main points Hare makes in the CNET article are that the passivhaus standard is (a) important, and (b) achievable with commonsense and inexpensive construction practices.

We were advised by a number of people to aim for a lesser standard given the state of our structure (a 100 year old, shoddily maintained, former corner store, abandoned for 5 years) and our extremely tight budget. Hare made a persuasive case that our national demonstration project (currently featured in a special series on Grist.org) should aim for the exacting passivhaus standard and Placetailor was the only firm willing to tackle the project on our low/middle income household budget. Placetailor's approach has potential to strengthen the effort to advance passivhaus by devising and testing low-cost methods that expand opportunities for builders and put passivhaus construction within reach of homeowners who may otherwise be priced out.

But there's no need or reason to argue the point beforehand. Isn't that what certification is for? The Pratt House will either meet passivhaus criteria or not and it is worrisome to see the process prejudged. Your comments give the appearance that personal opinion may play a role in certification, which I'm sure is unintended, but nonetheless deserves to be corrected. Otherwise, shouldn't we have cause to worry about JP Green House certification?

I understand that passivhaus is at a crucial juncture. The US Institute must preserve the integrity of the name, standard and procedures and some small sharp elbows will no doubt be thrown in the process, but Hare and Placetailor committed, young, hard-working, creative and effective passivhaus advocates and professionals are the wrong target.

Sincerely,
Ken Ward
co-founder, Jamaica Plain Green House
greenhousejp@gmail.com
http://www.grist.org/article/series/jpgreenhouse/
http://jpgreenhouse.org

by mrhare July 30, 2009 11:15 AM PDT
It?s unfortunate that PHIUS (Passive House Institute US) has resorted to defamation tactics when all thats called for is an intellectual debate. Placetailor believes in the performance standards that PHIUS promotes, and Lamonica?s article is a fair portrayal of our novel approach to meeting these standards. For example: Instead of shipping very expensive and exquisitely crafted windows from far away (Germany, Canada) we bought affordable recycled windows from the nonprofit Building Materials Resource Center down the road. Using standard weatherization kits and custom-made insulating shutters we intend to show our neighbors that they too can turn everyday windows into remarkable energy savers. The outcome of this effort will be published after we?ve completed a full year of datalogging and analysis of the Pratt House?s performance (early winter 2010). Stay tuned for the results!

by kklingenberg August 2, 2009 12:10 PM PDT

While Mike and I (Katrin) very much applaud your appreciation of and admiration for the Passive House Standard, we are very concerned about misinformation that is being spread in the name of Passive House, as Mike had expressed in his previous comment.

You are right with your statement that it is PHIUS's responsibility to "preserve the integrity of the name, standard and procedures" (otherwise it would quickly become meaningless). I like to say I am surprised that those who strive to reach one of the most rigorous standards out there and are called "committed, young, hard-working, creative and effective passivhaus advocates,? yet professionals (the same professionals who just characterized Passive House as appealing to ?geeks, but not the layman? and as ?just another barrier?) call it defamation if their project is looked at critically and held to those criteria by the institute that certifies and verifies.

We have not received a request to get the Pratt House Project certified and verified. Yet the JP Green Home is described here (http://www.grist.org/article/2009-07-29-promise-challenges-passivhaus-construction) as certified, if I understand that graph correctly. This is not the case and a false claim.

One reason might be that the process of certification here is fundamentally misunderstood. Projects are not certified based on the power bill after one year of occupancy, since this could be very much just be a reflection of user behavior.

Passive House Standard is superior to other rating systems that rely on checklists or prescriptive approaches. It is defined through predictable and verifiable performance standards. There are three criteria of quality and performance and you either meet them or you don't. It is pretty clear cut. The prediction is being done through modeling, mathematically balancing heat gains and heat losses in a building. Not any more geeky than balancing your checkbook, really. It allows the designer to not have to guess, which I think has happened here in this particular case.

It is not personal opinion that makes us think that your project does not meet the standard. We modeled many projects by now using the Passive House modeling tool PHPP and the measured results after one year match the predictions very closely.

Using modeling, I can tell in about 15 minutes where the house will most likely come in at in terms of energy consumption considering the materials? R-values, wall thickness, window specification and climate. Based on my approximate calculations, the Pratt home is likely to use about twice as much energy for space heating and cooling as a Passive House, even if they manage to legitimately reach the airtightness standard.

Back in March, a certified Passive House Consultant did conduct a blower door test and analyzed the Pratt House. His conclusion: Bottom line: it stands no chance of meeting the PH standards. It's an interesting project, and a good one, but it's not Passive House?. Many Passive House design principles have been disregarded in this project and some have been misunderstood. Passive Houses do not have to have all southern glazing, nor are windows to the East and West disallowed, they don't need masonry interior walls for thermal mass to work properly, the sun is not the main heating source, and the thermostat is set to 68 degrees Fahrenheit, not to 63. And it can be done in a very cost effective way.

Passive House has taken us to the next level of efficiency and comfort, and understanding that evolution and the reason why Passive Houses can reach those amazing levels of efficiency lies in systems design and components optimization. That is why it is superior to a prescriptive approach, or guess work "rule of thumb".

I like to respectfully disagree that we don't need modeling and that we don't need consultants. Every project is different. We need easy-to-use modeling tools and we need excellent consultants. The consultant is one of the most important and valuable people on the job as he/she is going to save you a lot of money.

I believe that this project is an admirable step in the right direction. It will be an excellent and efficient home even though it will be short of the Passive House standard. Placetailor has very recently sent someone to attend our Certified Passive House Training, to become a Passive House Consultant and to learn how to use the modeling software. It's unfortunate that in this case fundamental questions were asked later. We believe that Placetailor is on its way to taking future projects to the Passive House level. Keep up the good work.

Katrin Klingenberg

PHIUS
by euspos July 27, 2009 4:54 PM PDT
Wow, some good comments here. But, a lot of the energy related issues we see in US' houses today are due to really just poor craftmanship and speed, speed, speed (time=money).

We CAN build energy efficient, inexpensive houses if we just slowed down and did things right out of the starting block. Instead, we are smashing up houses with VERY questionable qualities, houses that will be OK for the first and possibly the 2nd owner, but after that - who cares? Therein lies the problem. Houses are built for shot term gain/profit as a "dwelling" and not for the long term viability as a "home". A very clear evidence of that is the lack of attention we pay to water/moisture management (like skipping on a few strips of metal flashing, and instead relying on caulk that always eventually will fail).

I was born and raised in Sweden, and even on our relatively northerly latitude (~as Alaska), there are tons of houses that require little or no supplemental energy to stay warm in the winter. They are just built upon good old proven simple standards like big (air tight) windows to the south. Place trees that drop their leaves in the winter to the south of the house (trees that provide shade in the summer while allowing the sun to provide heat in the winter). Put smaller windows on the north side. Use three-pane glass windows. Install doors that actually do SEAL. I think I still have to see an in-swing (the standard in the US) that actually is relatively air tight. And, do not even mention in-swinging French doors (easy to get to seal when they swing outwards).

Same goes for how insulation is "applied". A few good craftsmen do cut the batts and "stuff them" in properly, but most just "push the batts in, leaving large voids that wreaks havoc on insulating capabilities of otherwise good material. Same goes for vapor barrier (in cold/tempered climates). Who actually think that the kraft faced paper does anything? No, one has to apply a continous polysheen (or similar), seal all electrical outlets/boxes, stop using "bucket lights" (even the ones having an "air tight" seal), since they are really only great chimneys to shuffle heated air up into the attic (not necessarily bad for the house, but bad for the wallet). I could go on, but it is really not rocket science, it is just old established and tested practices, combined with professional pride in one's profession. A pride to do a good - a right/correct job - and not just "any" job in order to leave the job site after 8 hours.

I think unfortunately we've seen a bit of the same in the US auto industry (lack of attention to details and quality), but that is a whole other discussion.

Rant mode off.

I would say that professionals that are REALLY interested in this subjet, should take a few weeks traveling around primarily Scandinavia and Germany and just pick up on the already good, functional, tested, and widely implemented ideas. Do not go around and re-invent the wheel - when we've been able to both bike and drive a car for a long time on the subject of energy efficient buildings.