What is the difference between open and closed cell foam insulation?
Open cell foam is usually more suitable for residential applications for several reasons. Open cell foam is more flexible than closed cell foam. When the framing members expand and contract with the weather, open cell foam will flex with the wood, but closed cell foam will get hairline cracks where it was connected to the framing members because it is not able to flex. Another difference between open and closed cell foam is that, when used at the roof rafters, if a roof leak develops, the closed cell foam will not allow the water to weep through the foam because it is a vapor barrier. This can lead to rotting of the roof deck before the roof leak is ever discovered. Open cell foam is not a vapor barrier, so it allows the water from the roof leak to weep through the foam to the space below. After the roof leak is repaired, the open cell foam can be allowed to dry and its thermal properties return, unlike other insulations that must be replace when they get wet. In addition to these differences between open and closed cell foam, open cell foam is usually less expensive than closed cell foam.
Is open or closed cell foam better for residential applications? Why?
Open foam is better for residential applications. See the answer to “What is the difference between open and closed cell foam insulation?” for reasons why.
What is a vapor barrier and why do I need one in my walls?
A vapor barrier is also called a vapor retarder; this is a material that retards the movement of water vapor through a building element (such as walls, floors, and ceilings). It is important to have a vapor barrier such as building wrap or tar paper on the exterior walls of your home to prevent moisture from getting into your walls and causing mold and rot to occur. The building wrap should be located on the outside of the stud between the sheathing and the stud wall.
What is the best type of insulation to use in my walls and attic?
The best insulation to use in our hot humid climate is open cell spray-in foam insulation. This foam seals all air leaks and insulates very well in the walls and at the roofline. Unlike other insulations, it is an air barrier, so air infiltration is greatly reduced when using spray foam insulation. Creating an un-vented attic, using foam insulation at the roof rafters instead of the ceiling joists, will offer the most energy benefits. This turns the attic into conditioned space, part of the building’s thermal envelope. When this happens, the HVAC system no longer has to compete with the extreme temperatures found in vented attics, because most un-vented attics remain within 10 degrees of the home’s living space temperature. This allows you to downsize your HVAC equipment, saving money on the front end (by buying smaller equipment) and saving money every time the machine runs (because it is a smaller unit, using less energy). While spray foam insulation costs more than other insulations, its performance far surpasses that of any other insulation.
What is the best way to insulate underneath the subfloor of my home?
In most circumstances, the best way to prevent moisture from entering your home through the sub-floor and to insulate effectively is to have half pound, open-cell foam insulation installed at the sub-floor. Because this foam is an air barrier, the moisture-laden air of southeast Louisiana cannot move through the insulation to bring heat and humidity into the home. Also, the foam insulation will not fall out or become home to small animals that might like to live in other types of insulation.
What should I look for when purchasing windows for my home?
When purchasing windows for your new or existing home, you should pay attention to the type of glass used in the window. While the frame is important and vinyl is the best choice, the glass is even more important with regards to efficiency and comfort. The glass should have a Low E coating and a solar heat gain coefficient (SHGC) of no higher than .400. The type of Low E is called Low E squared or splutter coat. These are the terms used for the types of Low E appropriate for our southern climate.
What is Low E?
Low E stands for "low emissivity". Low E glass is coated with a microscopic, virtually invisible, metallic oxide layer that improves thermal performance. The primary function is to reduce the U-value by suppressing radiative heat flow. A secondary feature is the blocking of short wave radiation to impede heat gain. Low E is not just effective at keeping heat out in the summer, but at keeping heat in in the winter time. See the Efficient Windows website for more information:
What is more efficient to heat my home in the winter, a gas furnace or a heat pump?
A heat pump far surpasses the gas furnace in energy efficiency and even when gas prices were much cheaper, it was far less expensive to a heat pump than a gas furnace. An air-source heat pump can provide efficient heating and cooling for your home, especially in this hot humid climate. When properly installed, an air-source heat pump can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes. This is possible because a heat pump moves heat rather than converting it from a fuel, like in combustion heating systems. Take a look at the comparison of a heat pump to a gas furnace .
How does a heat pump work?
A heat pump's refrigeration system consists of a compressor and two coils made of copper tubing (one indoors and one outside), which are surrounded by aluminum fins to aid heat transfer. In the heating mode, liquid refrigerant extracts heat from the outside coils and air, and moves it inside as it evaporates into a gas. The indoor coils transfer heat from the refrigerant as it condenses back into a liquid. A reversing valve, near the compressor, can change the direction of the refrigerant flow for cooling as well as for defrosting the outdoor coils in winter. When outdoor temperatures fall below 40°F, a less-efficient panel of electric resistance coils, similar to those in your toaster, kicks in to provide indoor heating. This is why air-source heat pumps aren't always very efficient for heating in areas with cold winters.
