Cutting your energy costs is a great way to save money especially if you’re facing high electricity bills from the recent cold weather. The problem for some homeowners is that they might not be certain about the kinds of energy-related problems to look out for in their home. With that in mind, we’ve created a 4-part series about the Energy Efficient Home Improvements you can complete in 2014. This week, we’ll look at the most important one: insulation.
Your Thermal Security Blanket
Insulation is basically the warm security blanket for your home, and the more you have, the more efficiently you can maintain the temperature of your living space. It works through thermal resistance – it slows down the transference of heat through the home. In the winter, you want to slow the transfer of heat from the inside to the outside. In the summer, it’s the other way around.
Insulation is rated by its thermal transference resistance or “R value.” Again, the higher the number the better. Different materials also have different R values depending on their thickness and how they are installed. To find out how well your home’s insulation stacks up, check out Energy Star’s Home Energy Yardstick.
Throughout most of the country, the US DOE recommends at least R30 (about 1 foot of blown cellulose or fiberglass) for attic insulation and a minimum of a R13 (a bit more than 3 inches of blown cellulose or fiberglass) in the walls. While it’s possible to add more insulation to your walls, it can be complicated (and expensive).
Insulating Your Walls
One common way to improve your home’s insulation is to add rigid foam insulation to the exterior of your home and then install new siding on top of that. The problem is that the more insulation you want, the more deeply recessed your windows and doors become and you’ll need to add jamb extensions. If your home is very old and lacks insulation in the walls, you can blow cellulose insulation into your walls. Meanwhile, spray foam insulation must be sprayed directly onto the bare wall cavity. So, unless you are will to gut your interior sheetrock walls and use spray foam insulation, it’s not the easiest material for most retrofit jobs. Plus, it can also run from 60¢ to $1.20 a square foot, depending on whether you choose open or closed cell foam.
Insulating Your Attic
Unless they are finished spaces, most attics are designed to be part-outside and part-inside the home. They allow air to circulate and remove moisture to escape from the house while also supporting the roof that shields the living space from rain and heat from the sun. Attic insulation slows down heat loss during the winter when heated air inside your home warms the sheet rock and joists in your ceiling and that heat travels into the attic. A thick blanket inside your attic slows down that heat transference and keeps your living space at the temperature you want. Adding insulation to your attic is easy to do. It’s also hot, dusty, shin-bruising work, so you’ll want to be prepared with the right clothes, goggles, breathing mask, and shin guards.
You’ll need to know how much insulation you want to add. For example, if you want to go from an R-11 (3″) to an R-30 (9″) then you’ll need to add 6″ or about R-20. Again, different insulation types have different properties, and since you’ll be adding more insulation on top of an existing layer, you will not need “kraft-faced” insulation. To help calculate the full amount needed, you’ll also need to know the square footage of your attic. Be sure to air seal your attic first.
How much can you save? Some say it can be up to $600/year, but in reality it depends on your home and how you live in it. Energy.gov offers information on how to calculate what your home needs, or you can calculate a ball-park figure here.
All the same, increasing the thickness of your insulation from R-13 (3″) to R-30 (12″) has an immediate effect on how much more comfortable your home feels.
Insulating Your Basement
While attics can be hot and humid, basements can be cold and damp. Discomfort aside, it pays to insulate and vapor seal them properly to save money and be able to use them as a warm and dry space. Each basement has different insulating challenges but the basic premise to remember is to use a vapor barrier in place against the foundation wall to keep moisture in check. Broadly speaking, gluing 2 inch thick rigid foam (R-10) onto the foundation wall with a plastic vapor barrier over that is a good way to start.
One place that can be a problem is where the joist bay meets the mudsill, mainly because these spaces tend to be one of the draftiest in any house. Plus, there are many of them — one at each end of each pair of joists. Left alone, that can add up to a large amount of uninsulated and expensive space.
A common practice is to stuff batts of kraft-faced fiberglass insulation into these cavities. However, this usually results in moisture condensing against the rim or banding joist and ultimately causing rot. In the first photo on the left, the wood shows water stains from trapped moisture. To prevent eventual moisture problems, cut a piece of rigid foam as an insulator and vapor barrier. Caulk or foam this in place tightly against the rim joist (and seal where the mudsill meets the foundation block). Next, place a piece of sheet rock against the foam as a fire block (as per fire code). Lastly, you can begin adding your fiberglass insulation batts.
Insulating Your Duct Work
The last item you should insulate is your supply duct work. Insulated duct work keeps the temperature of air flowing from your forced air furnace at the heated (or cooled) temperature longer. While it was originally used for duct work that passed through uninsulated attics or crawl spaces, having insulated duct work cuts heating costs where older homes usually have bare metal supply duct work coming out from their furnaces. This reduces energy costs. Because heated (or cooled) air is traveling through the duct work, there’s no need for a thick blanket of insulation. R-6 is an average thickness. Home centers carry a variety of types of duct work insulation.
For everything you might want to know about insulation, we recommend that you visit Measure Guideline: Sealing and Insulating Ducts in Existing Homes.
Stay tuned for Part 4 of our energy efficient home improvements series next week!