Greening Your Home: Insulation

Heat moves through a home in 3 ways:

Radiation: transfer of heat from one object to another through the air

Conduction: transfer of heat between two objects that are touching

Convection: cyclical flow of air (hot air rises, displacing cold air which falls and heats up eventually causing it to rise again)



The R-value that you see when talking about insulation is a measure of effectiveness in stopping heat transfer. The higher the R-value, the less heat transfer there is.(It’s the opposite of the U-factor we talked about in the segment on windows.)



Is improving your insulation going to pay off? Try this calculator:

http://www.finehomebuilding.com/item/8998/payback-estimator-insulation-upgrade



Things to ask:

- Where should you focus your insulation efforts?

- How much insulation do you need?

- What type of insulation should you use?



Start with the basement/crawlspace if you have one. Warm, dry basements and crawlspaces can extend living and storage space, but tend to be sources of moisture, high humidity and mold. Spray foam is a fast and effective way to bring these areas into your conditioned space while sealing leaks between the foundation and the floor framing. If you are looking at creating a Net Zero Energy Use home (a home that produces as much energy as it uses), shoot for R-10 under the basement slab and R-20 in the basement walls.



Next, look at your roof. Air leaks in at the bottom of a house and leaks out at the top. A poorly insulated roof makes a house cold and drafty in the winter and hot in the summer. Air seal your roof using spray foam – this will also eliminate the need for roof venting which can be costly in complicated roofs. If you are blowing in insulation, make sure you seal air leaks and choose the right sealant for the job (example: Fire resistant seal needs to be used around the chimney). If you want to know where to look for potential air leaks in the attic, check for these: Recessed lights and electrical boxes, Holes for wires or pipes, spaces between the framing and chimney, plumbing or electrical chases, framed soffits that are open to the attic, drywall joints between ceiling and wall plates, and leaky joints in ductwork. The deeper your rafter cavities, the easier and cheaper it is to add insulation. If you are re-roofing your home, consider putting rigid foam board insulation on top of your sheathing. For a Net Zero energy home, shoot for R-60. Code minimums are woefully short of effective insulation – they are generally around R-25.



Last, insulate your walls. Opening up an existing wall to add insulation can be an expensive endeavor, but over the years, it has gotten better. Many contractors carry infrared cameras that can see if the voids in your walls have been filled with insulation without disturbing the walls. You can blow cellulose into wall cavities for a quick addition. If you are re-siding your home, consider installing foam sheathing on the outside of the home before re-siding. While codes only require as high as R-19 in cold climates, for a Net Zero Energy Use home, aim for R-40.



What’s in your walls now? It could be a number of things – or nothing at all. If you want to find out, check the electrical outlets – remove the cover plate and shine a flashlight into the space where the drywall or plaster meets the electrical box. If that doesn’t work you can drill a hole up into the wall cavity from the basement or down from the attic – use a piece of bent wire to help with probing. As a last resort, you can cut a small hole into a wall where it won’t be noticed and can easily be patched.



If your house was built prior to 1930 you may not have any insulation unless it was added later.



If your house was built between 1925 and 1950, you may have Vermiculite insulation. This naturally occurring mineral is a light weight, brownish-pink or brownish-silver colored pellet that was usually poured into wall cavities. If you have this type of insulation, you will need an asbestos-removal professional to handle removal and you should not disturb this insulation. You can consider topping off wall cavities with fiberglass, cellulose or pour foam.



Fiberglass is by far the most common type of insulation and has been used since the 1930s. This insulation can be yellow, pink, blue, or green. It also has questionable carcinogenic properties and will definitely make you itchy. Use gloves and a face mask when dealing with this insulation. Consider improving your insulation by filling empty spaces with blown cellulose or fiberglass or special types of pour foam.



If your house was built between 1935 and 1950 you may have Cotton Batts that are similar to dense cotton balls with a pilly or fuzzy appearance. While it is safe to touch, it is still best to wear a mask to protect your lungs. Also, don’t get it wet because it will take a long time to dry. Because it is a natural material, this insulation is becoming more popular with “green” builders. Consider housewrap or rigid foam on the outside wall to improve insulation.



If your house was built in the 1940s you may have Balsam Wood insulation. This is a type of wool made from balsam wood fibers. It is tan or brown and likely to be packaged in black paper batts. The fibers look similar to sawdust. Balsam wood is not a health hazard. Consider improving your insulation by filling empty spaces with blown cellulose or fiberglass or special types of pour foam.



If your house was built in the 1950s you may have Rock Wool insulation which is a fluffy, cotton like material that started out white or grey but is probably dark brown or black with age. This is a safe material and is starting to come back into popularity with “green” builders. It is not likely to settle over time and has the same insulating value as fiberglass or cellulose. Consider housewrap or rigid foam on the outside wall to improve insulation.



If your house was built in the late 70s, you probably have UFFI (Urea-Formaldehyde Foam). This is a light weight brownish gold foam that will likely crumble when you touch it. This insulation was banned in 1982 so the chances of elevated levels of formaldehyde existing due to the use of this product are slim. This foam has a high rate of shrinkage and deteriorates if it comes into contact with water. Unfortunately, this insulation is not a good candidate for removal – your best bet is to add rigid foam to the exterior walls under the siding to make up for voids in the wall.



I have mentioned rigid foam, blown cellulose and other insulation options. Let me take a minute to talk about what is out there.



Rigid foam works on any home because it is installed on the outside of the walls. It is attached directly to framing, sheathing, or siding, then covered with new siding, so it can be a costly process. Rigid Foams include EPS (Expanded Polystyrene) which runs about 45 cents per square foot and has an R-4 rating per inch (for comparison, fiberglass has an R-3.5 rating per inch), XPS (Extruded Polystyrene) which runs about 50 cents per square foot and has an R-5 rating, and Polyiso (Polyisocyanurate) which costs about 80 cents per square foot and has a rating of R-6.5 per inch and tend to be faced with foil to retard the flow of water vapor.



Pour foam is the most thorough insulation since it is injected into the wall cavity, flows as a liquid into the bottom of the stud cavity, then expands filling spaces and surrounding even the most complicated plumbing. Open Cell foams – which are permeable by water vapor have an R-4 rating while closed cell foams have an R-6 rating.



Spray foam, also known as Super Insulation, doesn’t settle and doesn’t give off toxic gas chemicals. Closed Cell foam has R-values between R-5 and R-6, and Open Cell has R-values between R-3.5 and R-4. Closed Cell spray foam initially installs at R-8, but it’s R-Value dimishes as the blowing agent evaporates, settling around R-6. Open Cell has a greater expansion rate, so less is needed to insulate a house. In either case, once you reach 5 inches of spray foam, you run into diminishing returns. Also, the cost of the foam is determined by the installer, not the manufacturer, so it pays to get many bids before choosing an installer.



The most common way to add in insulation is blown in cellulose or fiberglass. Cellulose is made of 80% post consumer recycled materials, has an R-3 to R-4 value and only costs about 25 cents per square foot of wall space, but it has a tendency to settle and leave voids. Fiberglass has an R-2.5 to R-4 value depending on the wall cavity and the density of the installation and will not absorb water. Fiberglass costs about 45 cents per square foot of wall space.



Another way to use insulation to improve your energy efficiency is to insulate your water heater! Wrapping a water heater with an insulation kit can cut your water heating bill by 5 to 10%. You can also insulate bare copper tubing for additional savings.