EnerPHit Good For Maine

The German Passive House standard for creating energy efficient buildings is not just for new buildings. This standard (which can lower heating by 85% to allow you to heat your home with equivalent of hair dryer on very cold day) can also be used on existing buildings to effectively eliminate a heating bill (extremely small bill- essentially eliminated) and remove your home from fossil fuel use.

Maine is one of our countries worst offenders when it comes to using oil to heat our buildings. According to the U.S. Energy Information Administration, EIA, "About four-fifths of Maine households use fuel oil as their primary energy source for home heating, a higher share than in any other State." The Northeast Biomass Working Group commissioned an analysis by Futuremetrics showing Maine as the fourth most petroleum state in the country with 70% of buildings heated with oil costing a billion dollars a year in exported spending shown here.

But the Passive House organization, Passivhaus Institut, has created a category for existing buildings called EnerPHit which adjusts the requirements for new building certification to account for the difficulty involved in renovating. Thus the air infiltration requirement for a new Passive House is maximum .6 air changes per hour but the retrofit standard is maximum 1.0. And the requirement for heating energy demand goes from 4.75 kBTU/ft2yr to around 8.

Most of the work to achieve the retrofit standard involves superinsulating the building shell. Replacing the usually energy inefficient windows with Passive House certified triple glazed ones with better thermal bridge free installation details is fairly straightforward compared to tackling the whole shell. Usually a combination of insulation methods is used specific to existing conditions. For instance it may be a good idea to spray foam insulate between studs or rafters or to add another row of studs to create a double wall and fill it with cellulose, etc. Some situations may be easier tackled by placing 8 inches of rigid insulation over the exterior walls and using the existing stud wall as a service cavity.

The important thing is for us to begin the process of eliminating fossil fuel use in this state and EnerPHit provides us with a metric to approach this problem with. PassivhausMaine will be holding an EnerPHit forum this September 27th in the morning at the Portland Public Library.

Passive House Windows- U Value

As stated in last PH post, the formula for window transmission losses is:

QT (in kBTU/yr) =  ∑(Uw, installed x Aw x ft  x Gt)  

Where Uw, installed is the U value (U= 1/R) of the window installed in BTU/hr ft2 F; Aw is the total window area in ft2 (square feet); ft is the temperature correction factor usually 1.0 and is unitless; and Gt is heating degree hours in kFhr/yr (thousand degree Fahrenheit hours per year) for your area.

Here's a good explanation of Passive House U value info:

http://www.passivhaustagung.de/Passive_House_E/window_U.htm

Looking at the U value installed formula: 

Uw, installed= [(Ug x Ag) + (Uf x Af) + (Ψg x Lg) + (Ψinstall x Linstall)] / Aw 

We see that this is the formula for the U value of a window-

Uw= [(Ug x Ag) + (Uf x Af) + (Ψg x Lg)] / Aw
 
-plus the linear thermal bridge coefficient of the installation edge around the window added before dividing by overall area of window (Aw). So to get the installed U value if we get an accurate uninstalled window U value which is possible when using a Passivhaus Certified window from the window label, we multiply the uninstalled window U value by area of window and add the product of the installation linear thermal bridge coefficient and the perimeter of window installation length and then divide all by area of window again.


The length of the installation, Linstall, is just the perimeter of the window. The linear thermal bridge coefficient, Ψinstall, of the installation is another matter. The definition of thermal bridge free construction is to have a linear thermal bridge loss coefficient of < 0.006 BTU/hr ft2 F.

You must model the whole window installation using THERM to get the coefficient. You subtract the separate ULdT calc of the window and of the wall from the calc of whole assembly to get Psi installed (one explanation ).

It's best to use a window installation detail that is either Passivhaus certified or closely resembles one. While it is possible to determine the U value of the window after gathering information from the manufacturer (explanation in this link ), it is generally much easier/safer to pick a certified Passivhaus window to begin with and just enter that data in your PHPP. 

As you might have guessed, it's not just necessary to buy good triple glazed Passive House windows but the detail for installation is crucial. If not installed with a thermal bridge free detail, you lose the effectiveness of the great windows. One person explained the relationship between all the insulation areas around a building by pointing out the doubling of insulation equals half the heat loss. Therefore, when you make a heat loss place, you have to massively increase your insulation everywhere else.

Next we'll look at how to approach the window details.

 

Passive House Windows- Energy Balancing

Here in Maine we need to design our buildings to the Passivhaus ( or "Passive House" as sometimes used in English speaking countries) standard in order to reduce our heating needs to almost nothing and to reduce our electrical energy needs as well. Part of this effort involves choosing triple pane well-insulating windows and installing them with thermal bridge free details.



The recommended window insulation value (resistance to heat transfer in hour square foot degrees Fahrenheit per British Thermal Unit or, hr ft2 F/ BTU ) for a window off the shelf is a minimum R 7.1 or an installed minimum of R 6.68. This R6.68 number holds true for the installed value of the glazing components of a Passive House door as well. These numbers are recommendations for Central European climate and thus a higher R value for Maine is certainly preferable. And certified Passive House windows are best.

Now part of a Passive House strategy to achieve low energy use is to gather as much solar heat gain as is practical without overheating. To this end the glazing in windows must be significant on south sides of the building and somewhat east and a bit on west sides with minimal on north. And the glazing in the windows must be shaded with overhangs tailored to each compass orientation to avoid overheating in summer and let lots of sun in, in winter. And this glazing must be designed to allow a certain amount of solar heat gain without reflecting too much so the heat passes into the building. This solar heat gain has a number called the solar heat gain coefficient or SHGC which represents the amount of solar heat allowed in with 1 representing all of it and 0 meaning none. A good SHGC for Maine would be between 60-62% or .60-.62 SHGC. A minimum of 50% solar heat should be allowed or .50.

Shading devices like overhangs or attached fins to keep summer sun out are important as a Passive House cannot have temperatures indoors exceed 77 degrees Fahrenheit for more than 10% of the occupied year (recommendation is 5% as global warming continuously upgrades the average temp).

A window is "energy balanced" if it takes in the same amount of energy in a year as it loses. It is "positive" energy balanced if it takes in more energy in a year than it loses and a Passive House wants to have a positive energy balance for each window without overheating beyond the above limit.The calculation for energy balance involves a calculation for window transmission losses (QT) and one for window solar gains (QS).

The formula for window transmission losses is QT (in kBTU/yr) =  sum of (Uw, installed x Aw x ft  x Gt) where Uw is the U value (U= 1/R) of the window installed in BTU/hr ft2 F; Aw is the total window area in ft2 (square feet); ft is the temperature correction factor usually 1.0 and is unitless; and Gt is heating degree hours in kFhr/yr (thousand degree Fahrenheit hours per year) for your area.

The formula for window solar gains is QS (in kBTU/yr) = r x g x Aw x G where r is the solar reduction factor plus the glazing fraction so a multiple of 4 factors and is unitless; g is the "g value" or solar transmittance also unitless; Aw is the area of the whole window unit in ft2 (square feet); and G is the global solar irradiation during heating period in kBTU/ft2yr (thousand BTU's per square foot year).

These windows are key whether building to meet new Passive House standards or retrofitting to meet the EnerPHit Passive House renovation standard. I'll talk about the meaning of the formula components and more in future. 

Creating a Peaceful Home

When I design a client's home new or renovation, I always work on clearing away the impediments to their relaxation. Eliminating barriers to peace and enjoyment are part of my work in this modern world of swirling information. I'm a minimalist in that I like to create spaces in which owners can naturally enjoy nature and light and materials without clutter. Everyday chores are exciting opportunities for the architect to celebrate living. The photo above is of a kitchen in a new home I designed in a neighborhood of small houses. By constructing a balanced, peaceful composition of utilitarian objects like counters and cabinets, fireplaces, floors and roofs and rooms, a calm atmosphere can occur.

I always strive for a dialogue with nature so that the act of living involves at least visual contact with the world outside. Materials can play a part by allowing feet and hands to touch natural objects and surfaces.

Knowing how to edit what is seen outside and what is not is a very important part of place creating and a peaceful home. This is why an architect can help you radically improve your sense of peace with careful cutting and pasting of walls and windows to bring out the best in your property.

Passive-Agressive House

Our current global crisis is based on the rise in CO2 levels. This rise is primarily a result of burning fossil fuels, mostly oil and coal. After Al Gore's movie in 2008, the green building movement took off and government officials and the private sector looked for a metric to mandate in order to reduce CO2 levels. They both found the LEED (Leadership in Energy and Environmental Design) system easy to mandate.

Standards like LEED helped start a wave of certified buildings that shifted our attention from construction efficiency to environmental impact. Government agencies in the USA now require many new construction projects to be LEED certified. While these buildings are a little more energy efficient and certainly more responsible with water efficiency, toxicity and some materials embodied energy use, they do not exactly drastically reduce our use of fossil fuels.

I like to think of the Prius as an example of a lot of embodied energy (the energy used to make the car) in an energy efficient product that ends up using more energy total (embodied and life time of low gas use) than buying a used car of medium size would (no new embodied energy as the car already exists). And buying renewable bamboo flooring from China shipped halfway across the world (high embodied energy in fuel used in shipping) is questionable. Embodied energy is a more realistic way to look at the impact of building material choices on CO2 levels.

Another embodied energy involves planning and how much energy people use driving to the building. It costs an additional 30-50% of the buildings active energy use to commute. Here is a good article on this embodied energy as well as the benefits of existing buildings.

So you could have the newest LEED building but located such that everyone commutes far and end up worse off than rehabbing an existing building in town.

But embodied energy, the energy it takes to make stuff and move it, is only a small part of the energy use problem. A better start to lowering CO2 emissions is to focus on fossil fuel use to create energy used to heat and cool buildings which accounts for almost 50% of our energy use. I try to think of what we can do to stop more coal plants coming on line in the US, China and India. In other words the forest-for-the-trees concept leads us to focus on cutting back our use of fossil fuels to heat and cool our buildings if you are an architect.

A popular metric for energy efficiency in building is the "Passivhaus" (passive house) certification. This rigorous standard developed in Germany focuses on reducing energy demand. Reducing energy demand implies not using a lot of energy to do this, hence, using "passive" methods rather than "active"(requiring energy) ones. The Passive House standard does this by addressing three definitions of energy efficiency: First, a building must be air tight so heat or cool is not lost or gained. Second, the building must have a very high level of insulation in the exterior envelope including windows, etc. so that heat or cool is not lost or gained and thus it has a very low heating energy use. And third, the amount of energy used for primary functions as in that used for the electricity must be very low as well.

This Passive House standard as it's called in the US is growing in use by governments in Europe to regulate energy use because that is precisely what it focuses on instead of everything as LEED type metrics do. Here, the use is growing especially at the green building house level.

Back in the 70's an energy crisis in the US led to a ton of experimentation with energy efficiency building design. Many architects created buildings with solar panels, passive solar heating through orientation and glass amounts, tromb walls, earth berming for insulation, solariums for circulating warmed air, and superinsulating or insulating the exterior building shell with much more insulation value than normal.

When Swede Bo Adamson and German Wolfgang Feist decided to create a very energy efficient standard for building in the late 80's they drew upon the work of the American pioneers of the 70's. Here is the wikipedia entry.

I worked for one of those American 70's architects here in Maine, Bill Sepe, who continues to build superinsulated buildings with air to air heat exchangers to provide fresh air to the super tight spaces. Passive house buildings are very healthy because of this constant air movement. As buildings became more air tight, we have not added the requirement for fresh air circulation and with the Passive House standard of .6 ACH 50 air tightness, the spaces require air circulation to be healthy. This requirement then makes a Passive House even more healthy than other buildings.

I'm a certified Passive House Designer through the Passive House Academy, based in Ireland affiliated with the international Passivhaus Institute in Germany PHI. The first Passive House in the US was built by Katrin Klingenberg in Urbana Illinois. She founded the Passive House Institute US, PHIUS, and became certified to train others to become certified. Unfortunately she wanted to be the only one in US allowed to train and a schism developed between the parent organization and hers. This has resulted in two certification possibilities here and I took the international one as best choice for long term. The PHIUS organization meanwhile has done fantastic work on moving passive house forward in the US so one can use resources from both organizations to get your Passivhaus project done.

Maine is a great place to build new or renovate to eliminate the need for almost all heating and thus, Passive House is a great metric to address this issue.