Our Advanced Insulation Package

Insulation is like a wool sweater for your house. It is what keeps you warm on a chilly winter day. Insulation and air impermeability go hand in hand. If insulation is the wool sweater for your house, the house wrap is your rain coat. We can talk about the air barrier later, but today I want to talk about insulation.

There are many different types of insulation on the market. At Arlington Designer Homes, we design our houses using different types of insulation for different reasons. We use a hybrid system which helps us maximize efficiencies. An insulation package that is correctly installed will have contact on all 6 sides: front, back, left, right, top and bottom.

On a typical construction project we will use Demilec Sealection 500 in the places where spray foam is a good fit. These places include the band board, bump outs and overhangs, and as part of the roof assembly.  Spray foam goes on in a thick coat and expands 100 times to fill all the nooks and crannies. It sticks in places where other types of insulation just won’t stay.

Another type of insulation we commonly use is spray-in fiberglass insulation or the BIBS system. This is another great insulation that fills all the cracks and helps to prevent air infiltration. Sometimes we will use a dense pack cellulose in the vertical walls, with the same benefits of the BIBS system.

If you have been reading my blog, then you know that the products we put in the walls and ceiling are just one part of the whole advanced insulation package. We use air sealing (check out our next blog for more on air sealing) to keep the air out and help the insulation perform the way it is supposed to. Advanced framing, proper ventilation, high quality windows and siding, and attention to detail are also all factors in making sure that our houses are properly insulated and extremely comfortable and energy efficient.

Insulation and Outsulation

We enjoy building custom homes and never build the same house twice. At the beginning of a new project, we worth with our customers to set specific goals for that house and then find the best  building products that will help us meet those goals.

In the two houses we are currently building in Falls Church, we have installed Dow SiS panels on the exterior of the house in place of more standard materials like plywood or OSB (oriented strand board). This structural foam insulation board serves three purposes. The first is that it acts as our house sheathing. It takes the place of OSB and eliminates the house wrap. The second purpose is that it serves as a drainage plane. With the SiS panels installed, there is no need to install a house wrap to drain rain and moisture -- it is installed with the sheathing. The SiS board, when properly sealed, serves as both a structural panel and house wrap. The third reason to install this product is that it provides 'outsulation'. This insulates a thermal break on the outside of the structure of the house.

Even the best-insulated houses have what are called “thermal breaks” or “thermal bridging.” This is when heat energy (hot or cold) is directly channeled outside of the building envelop by a break, such as a 2x4 stud in an external wall. A 2x4 stud has an R value (a measure of thermal resistance used to assess the efficiency of insulation – the higher the number the better) of about 4.3, which means that in relation to the rest of the wall system (which is probably around R-15), it is the weak link. The thermal break is a large area that helps heating and cooling energy escape from your home. Think about how many wooden studs there are in one 8 foot wall -- probably 8 to a wall and 36 studs in a room.  Calculate the energy loss (and increased heating/cooling costs!) throughout the house because of the thermal breaks caused by all of those studs, and you can see how putting more insulation on the outside of a stud could be beneficial.

Insulation and outsulation are important, but they are only part of the energy equation. A house is a whole system. This system includes the HVAC, the windows, the thermal envelope and the breathability of a house. More on these topics to come……..