FAQs Building Science
What is enough insulation?
The short answer is that there is probably never enough insulation in our homes because our building assemblies limit how much space we have to insulate to some degree. Insulation is really just a specialized product that either restricts convective air movement within a cavity (ex: fiberglass or cellulose) or provides a media in which air does not move through at all (open or closed cell foams). The other important attribute of all insulation products is that is provided a lousy thermal bridge; the phenomena where the warm side stays warm and the cold side stays cold. Older homes are usually quite deficient in properly filling voids and cavities in building assemblies. Some not so old homes might have some insulation but the clearances still allow for convective loops to occur and still newer but not so well built homes might have plenty of gaps and cracks that allows air into the structure regardless of the amount of insulation in the floors, walls and ceilings. A skilled builder/remodeler can assess and evaluate the thermal performance of your existing structure and make recommendations as necessary. It should be noted that with the current building codes in effect, most new homes are approaching the point where additional insulation may not provide proven payback over the life of the structure but this hardly the case for most of the existing homes which incidentally far out-number the amount of new homes built annually. Pros know that every remodel offers the opportunity to not only increase the operational efficiency of the house, it’s also an opportunity to make the home a more comfortable place to live. A true dual benefit.
Which insulation is best?
The best insulation is the type that is installed properly and is used in it’s intended location in a structure. Many types of insulation exist including fiberglass, cellulose, different foams and even used denim. The goal of all these products is to stop air movement through the material and to minimize thermal bridging, that is the materials property to be warm on one side and cold on the other. All insulation materials exhibit these properties, the real difference is how effective the insulation is which is referred to it’s r-value (usually expressed per inch or by combined inches.)
What’s the difference between insulation and air infiltration?
The biggest loser of energy in a house is air movement. This can be air moving in either direction since movement in general is bad. A proper air infiltration barrier minimizes the number of air changes per hour in a house and greatly increases the thermal comfort within the home; think, draft free rooms. Insulation is almost secondary to air movement. We want to first stop unplanned air circulation and then install the proper insulation type and thickness to maximize the temperature differential between outdoor and indoor air. That combination creates the most comfortable living space possible.
Why are my pipes freezing in an insulated space?
As mentioned above, more often than not it is air moving within a space that is supposedly properly insulated. It usually is not an issue of the insulation not being present but a factor of air movement and/or the insulation being installed on the “warm” or incorrect side of the pipes. Water and sewer piping must be insulated so they are contained within the thermal envelope and are not subject to cold air washing over them which would eventually cause the pipes to freeze.
Are there different types of spray foam?
There are all sorts of brands of spray foam, both available to the pro as well products that can be purchased in home centers. The real difference in professionally applied foams is that there are open cell as well as closed cell foams. Open cell foams allow for moisture diffusion (water vapor movement) and closed cell foams allow no water vapor diffusion. This creates essentially a water barrier membrane. This is very effective in some installations and not such a good idea in other building assemblies. Leave this determination up to your contractor and insulation specialist. The wrong choice can have serious non-intended consequences.
Why is attic ventilation important?
All homes create a fair amount of moisture from activities within the house including cooking, bathing, laundry, houseplants and gas combustion equipment that is non-vented such as cooktops. Air movement and temperature/humidity differential between the inside and outside can drive moisture into building assemblies including attic spaces. In an uninsulated attic, the moisture escaping the living space has the potential to condense on colder surfaces and turn into liquid water. A ventilated attic has the ability to carry any water away from the enclosed space, essentially keeping the surfaces free of water accumulation.
Should my crawlspace be insulated?
In our climate where it is cold in the winter and warm in the summer, it is best to seal and insulate crawlspaces for several reasons. The typical crawl space introduces water into the home from the earth beneath as well as migrating through the sidewalls. In addition, in a warm, humid climate, a ventilated crawl brings warm humid air into a cooler space in the summer and that air easily condenses on the colder surfaces in the crawl creating unintended water to accumulate. By sealing any air exchange from the outside, adding an appropriate amount of insulation and providing a little conditioned air into the crawlspace creating an environment that is within the thermal envelope and thus allows for a space that is warmer and dryer, much like the rest of the living space. The second advantage is that this is a permanent installation and does not require seasonal opening and closing of the foundation vents, an activity that is as antiquated as the science that used to support it.
What is housewrap? How does it work?
Housewraps are a barrier that keeps the house dry from water outside the home and also creates an air barrier, effectively reducing drafts and air movement in the exterior walls. Wraps come in many different brands and compositions but they all share the water and air barrier properties. Where they differ is in the amount of water vapor that is permitted to pass through the wrap. This has an effect on how well a wall might dry out if interior house moisture moves into the wall cavity. Housewraps are known in the industry as Weather Resistant Barriers and are the primary defense against bulk moisture reaching wall cavities since it is assumed all sidings and exterior finishes have the potential for leakage. The key is a properly installed continuous barrier with no gaps, tears or holes and that the laps/flashings and sealants are all installed to the manufacturer specification. Only then will the WRB be sufficient to insure permanent protection of the wall section.
Why does my fireplace not draft correctly?
Fireplaces can be problematic from the start if not properly designed and constructed and this probably accounts for most of the performance difficulties seen. The firebox opening, throat, smoke shelf, flue size and chimney height all must work in unison for a wood burning fireplace to draft efficiently and not backdraft (smoke). A good drawing fireplace will take very little to warm up to create the convective draft that pulls smoke up the chimney. Another but less frequently observed problem is when the fireplace was built well enough to accommodate the original construction but then is tested when replacement windows are installed for instance. The “tightening” of the house might not allow enough air into the home to offset what is going, or trying to be pulled, up the chimney. Fans including larger kitchen range vents can also create competition for the chimney to provide a sufficient draft to maintain a draw and not backdraft. A solution to this is to attempt to provide more air into the home by installing a permanent makeup air duct or by simply cracking a window when that backdraft is observed. Gas fireplaces and gas logs tend to be a little less finicky but nonetheless important to make sure combustion gases are not being pulled back into the home. This is quite unhealthy as well since the gases contain carbon monoxide and a lot of water vapor.