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Health & Fitness

So You've Decided to Add Insulation

A discussion on how insulation works and how to decide what type to purchase.

So you’ve decided your home needs an improvement in insulation.  No problem you just call a contractor and have them come in and take care of it or you run down to the big box home improvement store, buy some insulation and put it in.  Problem solved. 

Before you make a decision though, it is important to understand how insulation works.  Heat is transferred in a variety of ways through your home.  There are three major types of heat that affect your home.  Radiant heat, convective heat and conductive heat.  Radiant heat is heat that is emitted from a heated object such as the sun or your body.  This heat radiates out from the body in waves and when it hits another object it is absorbed or reflected.  This is the heat that makes the asphalt hot in the summer and is the heat that Low-E windows are designed to reflect.  This heat is also what causes attics to heat up in the summer.  Houses with white or silver shingles are able to reflect a great deal of this heat while dark shingles tend to absorb this heat.  In our discussion of insulation this heat does not come in to play to a great extent. 

Convective heat is heat carried by moving air and in most houses is the cause of a great deal of heat loss.  The heated air moves throughout your home and escapes the home through any gaps and cracks that are available.  Convective heat is also the heat that gives the allusion of drafts around windows and is behind the premise behind that “hot air rises”.   The reality is that hot air rises only when the air is allowed to move freely.  In homes that are well sealed this air movement is greatly diminished and therefore a more constant heat is found throughout the home.

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Conductive heat is heat that is transferred through a solid body such as a frying pan or in the case of your home through the drywall and other building materials.  The purpose of insulation is to slow down the transfer of heat 5to the outside of your home.  Indoor heated air reaches the exterior of the home and heats up those surfaces through conductive heat.  When it reaches the exterior of those surfaces it naturally wants to become convective heat and move away from the home on the air currents.  This is where insulation comes in.  

Insulation, when properly installed has tiny air pockets which stop the transfer of heat.  The heated air reaches the exterior of the solid surface and has three choices.  It can remain conductive heat and transfer through the insulation, except for the fact that the air pockets in insulation do not conduct heat well and the insulation itself is not dense enough to conduct heat.  For this reason you do not ever want to pack insulation in too tight when installing it.  The second option for the treated air is to turn in to convective heat but if the insulation is installed tightly to the exterior surface there is no room for air currents to begin moving.  This is also the premise behind the insulating success of double pane glass.  There is not enough room between the two panes for air to start moving but there is enough gap that the air does not conduct heat through to the other side.  The last option for the heat is for it to stay where it is and thus stop the flow of any other heat from escaping the home.  This is the option which we are trying to achieve with insulation.  It is also important to note that prior to any insulating project you should seal any penetrations going in to your attic as these penetrations allow heat to enter the attic as convective heat and this heated air will be allowed to pass through the insulation and escape the home.  Now the question is what insulation product should you buy to help out your home?

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If  you are looking for the best product to insulate and seal your home it is spray foam.  This product has a high R-Value and also eliminates all air leakage in the attic which will reduce the feelings of drafts in your home and will reduce air entering the home through building products in the basement.  The drawback to this product is that it can be expensive and due to the equipment involved it is not something a homeowner can do on their own.

The best option for your home is blown in insulation.  It provides an even coverage,  it has air sealing properties and it is easy to install.  My preference is cellulose as it is made of recycled newspaper, it is not itchy like its fiberglass counterpart and if the homeowner is interested they can install it themselves.  It only requires two people.  One to load the machine and one to blow the product into the attic.  It is also cheaper than fiberglass batts or rolls and most of the big box stores will let you use the machine for free as long as you buy 20 or more bales.  Blown in insulation can also be installed in an attic without insulation or over the top of existing insulation.

Probably the worst option for insulation is the typical fiberglass batts thet are found in many homes.  Though its insulating properties are good when properly installed it is rarely properly installed and leaves many opportunities for convective air to form and thus take heated air away from your living space. 

Hopefully this article has armed you with the information you need when tackling this important energy conservation measure.

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