Tuesday, December 12

Are You Heating The Neighborhood?

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A typical house caught in the act of heating the neighborhood. This was taken with a thermal imaging camera which shows temperature differentials between surfaces. Light colors are warmer and dark colors are colder.

So, are you heating the neighborhood? The short answer is most likely a resounding “yes.” Even if you keep all of your windows and doors closed during the whole winter, your house was designed to keep just enough of the heat you pay for to keep you somewhat comfortable. Most of us have learned to deal with this issue by putting on warmer clothes, or putting plastic on the windows. This last method is really difficult to implement on a door, although it might serve as a great practical joke.

The issue is with home design and building methods. Having built and remodeled homes for the last 20 years, I can tell you the insulation types and methods of installation always take the back seat to how the final product appears. If a newly built or remodeled home looks good when it is finished, no one really pays attention to how the insulation was installed and most have never even heard of the need to air seal. In fact, many carpenters still believe a little air leakage is good for the house and it’s occupants. This couldn’t be further from the truth. While fresh air in the house is a good thing, uncontrolled air leakage simply means you are heating the neighborhood.

Standard building practices also create something called “thermal bridging.” A thermal bridge is created whenever a continuous path is created between the exterior and interior of a building. This is not done intentionally, but it happens because of how a house is constructed. A perfect example of a thermal bridge is the framing of an exterior wall. Because the exterior, as well as the interior, wall materials are attached to the framing of a house, the framing becomes a bridge for heat and cold transfer. Your wall may have insulation in the cavities between the framing, but because wood is a poor insulator, there are cold and/or warm spots all along an exterior wall wherever there is a framing member. The picture to the left is a thermal image I took of an exterior wall using a Flir thermal camera. You can not only see the framing of the wall (blue vertical lines), but you can see the intensely cold spot between the wall and floor junction. This is because the insulation stops 1 ½” above to floor (there is a horizontal framing member called the bottom plate.)

Here is a rule of thumb for how heat moves around a space; heat will always move from a warm spot, to a cold spot. In other words, if the surrounding air temperature is 70 degrees and the area pictured is about 45 degrees, the heat from the air will always flow to the cold spot in an attempt toequalize. Because there is a gap or a thermal bridge, the cold spot will never become equal in temperature to indoor air, which means the warm air in your house, the stuff you pay for, will always be trying to heat that cold spot.

Attics are an even bigger neighborhood radiator. The majority of a building’s heat loss happens through the roof. This is because the majority of insulation in an attic is inadequate or poorly installed. According to standard modern building practices, an attic should be insulated with R-38 insulation. This is typically anywhere from 10”-12” of insulation and is placed between the ceiling framing members. The insulation is most likely fiberglass roll insulation, which doesn’t fit very tightly in the cavity. Add to this the fact it is rare to find ceiling framing much wider than 7 ¼” and electrical, plumbing and heating penetrations into the attic are rarely sealed. All of this adds up to a Swiss cheese effect. There are many ways for heat to escape. Remember, you pay for that heat.

So, what are the solutions? After all, building a house according to most local building codes is like getting a “C” on your report card and even at strictest levels of enforcement leave homes leaking like sieves. In some cases, I’ve seen building inspectors come in to inspect a building once after all of the rough framing is completed and once after all of the finishes are completed. No insulation inspections!

The solution is to get yourself educated. You need to be your own advocate because it will be you living in that house, not the inspector or the tradesmen. The following are some useful bits of information and building techniques which will create a home that’s not only more comfortable year round, but will cost less to heat and cool. It may be a bit more expensive in the beginning, but you have to look at the overall lifetime of your home. It will cost you more in the long run in utility bills and a dirtier world.

Let’s start with the attic. If you’re building a new home, or just adding insulation to an existing home, before you insulate, make sure all holes are sealed up tight. Electricians, plumbers and HVAC guys will often drill holes much bigger than they need to be in order to fit their fixtures. Make them seal those holes with expanding spray foam. This goes for piping, heating ducts (which should be insulated throughout the building) and electrical junction boxes. Junction boxes are a bit tricky. They are full of holes which will let your heat escape, but if you use spray foam on these, the foam will get into the box. Not a good scene. However, if you caulk all of the holes, or use tape around the exterior of the box, you can spray foam these, as well. The next step is to provide air passages between you attic and your building’s eaves. This is a necessary step because your attic does need to breathe. In fact, in a properly installed attic assembly, the temperature in the attic should be approximately the same as the outdoor temperature. This prevents condensation and mold growth. A building product called a baffle will do the trick. It is typically made of polystyrene and it is stapled to the underside of the roof sheeting, right where the roof framing meets the wall framing. By extending the baffles over the outside of your building’s walls, you will ensure a proper air channel. Once all of your holes are sealed and air baffles are installed, you can get to insulating. New construction should have insulation with a paper face on one side. This side should face the living space and should be stapled over the face of the framing members, in effect creating a “solid” barrier against any moisture found in the air inside of the house. Have the insulation contractor tape all of the seams of this paper facing. If you are retrofitting an existing attic, the insulation should not have this paper facing. There is typically no proper way of installing this vapor barrier in existing attics. Once the roll insulation has been been installed, it is time to address the gaps created by the framing. This is where loosefill insulation comes in handy. Loosefill is, just like it sounds, a form of insulation which is blown into an attic, and falls loosely to fill in any gaps. This will fill in all of the gaps which the roll insulation can notfill, including framing gaps. Overfill all areas because this stuff will settle over time. In fact, if you fill all gaps and blow in additional inch over all of your insulation, you will have a really well insulated ceiling.

If your building has a flat roof, insulating is a bit trickier. Simply stuffing your roof/ceiling framing with insulation will not be adequate. In fact, this may create a situation where the warm, moist air from the interior of the home condenses on the underside of your roof sheeting and creates a serious moisture problem. In the case of a flat roof, your roofing contractor should install at least 2” of rigid foam board insulation on top of your roof’s sheeting before they seal the roof. This moves the cold area, or where condensation will occur, to your roof, which is an adequately waterproof spot.

Heat escaping along a foundaion wall. The dark blue stuff on the left of the glowing line is snow.

Next to an attic, the second area prone to most heat loss is the foundation. This may seem counter intuitive, but remember, heat moves from warm to cold. Because your foundation and basement floor is made of concrete, or other masonry products, it’s a gigantic heat sink. All masonry products are considered high mass thermal storage materials. This simply means they hold their temperature well. If the foundation is surrounded by cold soil, it will be cold. Because it is permeable, putting roll insulation in direct contact with any masonry product is not a good idea. This type of insulation soaks up and holds moisture. Again, the neighborhood mold and fungus spores would really love you for their new home. The best solution here is to install rigid foam insulation around the entire perimeter of the foundation. Look for the stuff with the highest R value and glue it directly to the foundation with a high quality glue which is both moisture resistant and compatible with foam building materials. Pay attention to that last parameter. There are some glues which will dissolve foam.

The walls of a building are the next consideration. If you have an existing home, this may not be the most economical place to spend your money. It is somewhat difficult to insulate a wall which has been finished on the interior and exterior, especially if it already has some insulation in it. If there is no insulation in the cavity and you have some extra money in your home improvement budget, the best approach is loosefill cellulose insulation. The installation is a bit intrusive because holes have to be drilled in your walls. If after reading this, you’re still game, find a good reputable contractor who can do something called a densepack installation. This involve sticking a hose into each framing cavity and mechanically blowing in cellulose insulation to achieve a high density (approximately 3.8lbs./cu.ft.) There ais expanding foam insulation available which are installed in similar fashion, but be aware; expanding foam can blow out plaster or drywall if not installed properly. Cellulose will not do that, and it’s much cheaper.

If you’re building a new house, or are doing extensive remodeling on an existing house, this is your chance to get rid of the thermal bridges. The only thing that has to be done is to add horizontal framing strips across all of your exterior walls. Insulate the walls well, then find a supplier who carries something called an RC channel. This is most often used in situation where sound deadening is required, but works great to break the thermal bridge. It is made of metal and comes in standard lengths. You simply screw these across you exterior wall framing and screw the drywall to the channels. These allow you to keep your drywall from coming in contact with the framing of your exterior walls, which prevents outdoor temperatures from being transferred to the interior of your wall.

Leaky door bottom

So, your walls are super insulated, the thermal bridging has been broken, but there are still holes in your walls. These “holes” would be your doors and windows. Although not considered to be high priority replacement items on most energy expert’s lists, these should be carefully considered, especially if you are already planning a remodel or a new building. While your wall may have a total assembly value of say R-19, your single pane wood window with storms on the outside has an R value of about 1.5.

Cold window on a warm wall.

There are many options available. For the most part, vinyl windows are the cheapest and perform as such. In my humble opinion, vinyl windows should be totally discontinued. Vinyl is a poor insulator and experience too much movement during temperature shifts. The big problem with this phenomenon is it moves at a different rate than the glass it hold, therefore the seals on the window will eventually stop sealing. You get foggy glass, cold drafts . . . well, you get the picture. Wood has been the traditional choice for windows for many years. It is durable, especially if covered on the outside with aluminum capping. Wood windows are not a bad choice, but the material is still a poor insulator. If you decide to use wood windows, make sure the installer uses low expanding foam to fill in the gaps between the window frame and the wall framing. This will ensure an air tight seal, at least around the window perimeter. The best of the best, in as far as window and door materials, is fiberglass. These tend to be a bit more expensive, but will outperform any other material. Fiberglass is a really good insulator and, more importantly, because it is essentially glass, it expands at the same rate as the glass pane. Add to this a triple pane with argon or krypton gas and you have the Cadillac of windows.

Door are essentially the same as windows. They are a necessary evil, in as far as a barrier against outdoor temperatures, but with careful choices and proper installation techniques, the losses can be minimized. High quality steel skinned doors are not a bad choice, however steel is a great conductor of energy. Heat and cold flow through easily. Most manufacturers minimize this by separating the exterior skin from the interior by using a foam core and a wood perimeter. As long as the seals are high quality (usually magnetic seals perform the best), a steel door can last a long time and keep most of the outdoor temperatures, outdoors. Fiberglass skinned doors have come a long way. They have become quite stable and are great insulators. About 12 years ago, I installed a large fiberglass double door. The expansion and contractions in these doors was amazing. While the sun was shining on them, the gap between the two doors was about an 1/8”. After a cool night, the doors shrunk so much, the gap had widened to about 3/8”. That was then, this is now and most manufacturers have improved their product lines considerable.

The bottom line is, if you do your homework and pay attention to what your contractors are doing, your new or remodeled house can not only be beautiful, it will keep you comfortable and won’t cost a small fortune to keep you that way. A few extra steps along the way can make a huge difference.




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