When To Use Underfloor Insulation

Underfloor insulation is an often overlooked area of the home that deserve just as much attention as other exterior walls.  It has been said that up to 25% of your home’s energy loss can be attributed to poorly insulated floors.  However, there are certain circumstances when underfloor insulation is NOT necessary.  For example, if your basement is finished and heated, then insulating your main floor will not likely improve your home’s efficiency, unless you are trying to block unwanted noise from entering or exiting the basement.  In which case, not only should you use underfloor insulation, but an underfloor sound barrier such as mass loaded vinyl as well.
Another reason why you may not need traditional underfloor insulation is if you have concrete floors.

Types Of Underfloor Insulation

If you do think you will be able to increase your home’s energy efficiency by insulating the floors there are several types of materials that you can use.  Depending on you access to the floor joists (if you have an open basement) and the number of pipes, duct work, and wire conduit, you can choose a material that is cost effective and easy to install.

• Batt Insulation – Made from fiberglass and backed with paper, Batt Insulation is one of the most cost effective methods of insulation on the market.  It is extremely common in modern construction, and is favored because it is a flame retardant material.  The disadvantages of this type of underfloor insulation is it is somewhat bulky to manage and install especially in tight areas, or bays with multiple pipes and wires.
• Foam Board Insulation – Much easier to cut and manage, foam board insulation is a rigid foil backed underfloor insulation that comes in 4×8 foot sheets.  Easily cut with a straightedge and utility, knife, foam board can be measured and cut outside of the work area.  The disadvantage of foam board insulation is that it requires extra work sealing all of the cracks and seams with tape and silicone to ensure you eliminate all of your inefficiencies.
• Blown Insulation – The easiest and one of the most effective ways of insulating hard to reach areas is to use a machine to blow in cellulose or fiberglass fibers.  It does a great job of getting around pipes and wires, and creates a good seal from bay to bay.  The disadvantage of blown in insulation is the cost.  You must either rent a machine your self and learn the trade, or pay a professional to do the job.  Both require time and energy.

Comparing Underfloor Insulation

All insulation is compared with a metric called thermal resistance, or “R” value.  The higher the R value the better that type of insulation is at insulating your home. Therefore, underfloor insulation should be purchased based on it’s R value, not it’s thickness, density, shape, or look.  All of the above methods have an R value between 3.5 and 4 per inch, so the best underfloor insulation method is the one that fits your budget and space constraints.