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WE’RE ON NPR!

Jessica Gould of WAMU came by the house on Friday and did a piece on the house during Morning Edition today. Here’s the link: http://wamu.org/news/11/06/27/bethesda_home_is_areas_first_passive_house.php

Highlights from Innsbruck: The 15th International Passive House Conference

June 2, 2011

I have just returned from the annual Passive House conference in Innsbruck, which included around 1200 architects and builders from some 46 countries. The Passive House approach has truly become global. While fresh in my mind, I have tried to summarize—in no particular order—some highlights below. A long post, but there were some 40 presentations!

 More sophisticated designs. As European architects get used to manipulating the requirements of the Passive House modeling software, there is an increasing amount of variety in the designs they are producing. Design has evolved well beyond the “simple German box.”  I saw schools with large arrays of skylights over gymns and public spaces, apartment buildings oriented with the long axis facing west, and buildings of all shapes and sizes— all being features that once seemed deal-killers in passive house design.  Yet today architects have found ways within the program to compensate around these features.  Such is the beauty and flexibility of the approach.

You can’t get to Net Zero without going through Passive House. Not unless you have no budget constraint concerns. A number of the presentations demonstrated that unless you bring your building envelope up to Passive House levels of efficiency, the additional renewables required to get to Net Zero become cost prohibitive. 

“Nearly Zero” Buildings. A new European directive onenergy performance of buildings requires all new buildings to be ‘nearly zero-energy’ by 2020. With this in mind, Europeans are moving to the next frontier: the Energy Plus house. In this approach, buildings are built to Passive House levels of performance, then through the use of renewables (primarily photovoltaics tied back into the grid), they are taking these buildings to the point that they net an annual surplus of energy. The City of Hannover, for example, has already begun Zero:e Park, a three phase project to build 330 homes that meet the Energy Plus requirement. With careful zoning guidelines that ensure maximum passive solar orientation and solar gain, they otherwise impose no design restrictions upon architects and developers beyond the performance standard of Energy Plus. Programs such as these will surely be studied carefully by Arlington County and other jurisdictions that are now planning for model energy developments incorporating the Passive House approach.Photovoltaics often make more sense than solar thermal panels—even for solar hot water. The arguments:

• PV panels maintain the same efficiency relative to solar exposure year round, while solar thermal efficiency drops significantly in winter months.
• Solar thermal panels become decreasingly efficient as the array grows larger due to increasing system temperatures and storage areas. There is no comparable drop-off of efficiency for PV.
• Annual maintenance costs for solar thermal are significantly lower than plug-n-play PV’s. These costs should be included in any comparative cost analysis.
• PV panels can be much more efficient at making hot water when tied to heat pumps, which have the added versatility of providing air conditioning in the summer months.
• Over time solar PV panels will continue to improve in efficiency, yet solar thermal panels will remain more or less at present levels. This should be a consideration in long-term planning.

I am sure there will be many who will take issue with these arguments. I’m happy to share the abstract of the presentation with anyone interested, so that they can weigh the evidence for themselves.

Advances in Retrofitting. Techniques for the retrofitting of existing buildings, both on the inside and the outside of the exterior walls, are continuing to develop.

• We saw examples of historic structures that had been insulated completely on the inside, leaving exterior walls restored to their original look. 
• In another case, a historic structure with a stucco finish had an insulation applied to  exterior walls and roof, with a new finish identical to the old; only the building was now 3% larger, but enlarged in scale with the original building!
• We saw another building which had been insulated on the exterior with vacuum insulated panels (VIP’s). These prefabricated panels are made up thin outer layers (+/- 3/8”) of XPS foam for protection and middle layer (1”) of vacuum panel. These panels are incredibly efficient and get about 8 times the efficiency of EPS, cellulose and fiberglass. But they cost approximately 2.5x as much as those. In this case, the building was carefully measured beforehand and panels made to the exact shapes required.
• On the tour following the conference we saw two schools that had been retrofitted to Passive House standard. In one case the work involved a complete gut and restoration of the existing building. The other left the interior of the school largely intact and the exterior insulation and new mechanical system were installed over two summer vacations and school was never interrupted. Heating and cooling costs were cut over 90% for a budget I derive from the architect’s numbers to be about $50/sf.
• Realizing the importance of retrofitting existing building stock, the Passive House Institute has come with a new standard addressing retrofits: the Passive House EnerPHit Standard. Because built-in thermal bridging issues and the inability to address foundation issues make it impossible for many existing buildings to achieve the  Passive House performance standard, this alternative standard evaluates buildings on a basis of the component parts of the PH standard: air infiltration, ventilation systems, envelope insulation, but allows a somewhat higher level of  annual energy use per square foot.  So while it remains at bottom a performance standard, it also incorporates a prescriptive approach to the key building components.

New Products. We also saw the range of products made specifically for the Passive House market continue to expand.

• There is increasing competition in the window market, with a new generation of lower cost windows with thinner frames that meet the highest PH window rating. And the number of companies jumping into the Passive House market continues to grow. Energate, one of the very best, has purchased the H Windows factory in the US with plans to begin building their windows in the US. At present they are selling their German-made units in the US at basically the price they charge in Germany (discounting shipping costs) as a way of growing the US market.
• More companies are making combination ERV/heat pump/hot water units— the so-called “magic boxes” — designed specifically for the Passive House market.  They are quite expensive, but may be competitive when you consider they replace your heating and cooling unit, your ventilation unit and your hot water tank. Some may be available in the US as soon as next year.
• More companies are jumping into the market for slab and basement wall insulating systems. And they are truly systems— made up of modular blocks as well as sheet goods. The blocks are assembled to create the formwork for exterior footings, and to contain the underslab insulation. A crew lays these out in a matter of hours in the manner of Lego blocks, then drops in the steel reinforcing and then is ready to pour concrete. The walls are subsequently erected with insulating concrete forms (ICF’s), also assembled like Legos. The difference between these and US-made ICF’s is that they are made asymmetrically, with a smaller amount of insulation on the interior face and a larger amount of insulation on the exterior. The purpose of this is to allow the building to take greater advantage of the thermal mass of the concrete than the US systems do. This is particularly important for Passive Houses where summer cooling is a factor.

 New Studies on Comfort and Air Quality. Several presentations brought out new studies on interior comfort and improved interior air quality in Passive Houses, all of which bore out earlier evidence of significantly higher performance in these areas for Passive Houses. CO2  levels and indoor relative humidity levels were consistently lower, and user evaluations of overall comfort were consistently higher, often in the 90% range.

The Growing American Presence. The US was represented this year by over 50 people, including 10 students from Miami University. This is a jump of about 500% from the 2009 conference. In addition, three Americans, Carley Coulson, Graham Irwin  and Virginia’s own Adam Cohen, presented papers on their projects.

 The conference proceedings should be available soon from the Passive House Institute.

Comparison of projected energy costs between this house and a hypothetical identical house built to the Energy Star standard

During Earth Week we were asked to do presentations at NIH and DOE on this house.  In preparation for that I revisited our cost numbers and our energy numbers for the house and put together a comparison of this Passive House to a hypothetical identical house built to the Energy Star standard.

Here are the assumptions I made:

•  The Passive House components of this house increased the cost by 8% over building it to the Energy Star standard. This is based upon actual construction cost figures from our subcontractors.
• Both houses are financed at 20% down in a 30 year jumbo mortgage at an interest rate of 6.37%.
• Downpayment savings of the less expensive hypothetical Energy Star house are invested at 3% per annum, and the annual income applied to the mortgage payment.
•  Projected Passive House energy numbers are derived using Passive House energy modeling software, which has proven a very accurate predictor of actual energy use in Passive Houses around the world.  To convert that to predicted energy costs we used current Maryland energy residential energy rates. While we are confident that these numbers are broadly reliable for our house, actual energy numbers may vary depending upon user habits.
• To get the comparative predicted energy costs of the hypothetical Energy Star house, we used a factor based upon the comparative HERS ratings of Energy Star and Passive Houses. That factor is assumed to be 85/30 in this case.
• We then put together the following graph showing annual cost of ownership numbers (mortgage cost + energy costs) of both houses. We looked at two scenarios: one where energy rates increase at a 1% annual rate and a second where they increase at a 5% annual rate. We think both of these rates of increase are conservative given the volatility of today’s energy market.

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