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Save money, improve comfort and cool the planet.

Good Planning Saves Money

It's critical to understand both modern building science and how your building was constructed before deciding how best to tighten the "building envelope" (foundation, walls and roof), especially if planning a DIY project. Learn about building science.

Regardless of our attention to detail, we can't see inside closed cavities, such as walls, finished attics, vaulted ceilings, interior soffits, etc. 


To determine how leaky your structure's envelope is and how best to tighten it, it's best to hire a building performance auditor to use an infiltrometer (or blower-door) and infrared (or thermographic) camera to identify hidden gaps, holes and voids.  Ask for the photos so you can methodically address them.

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Don't be this guy!

Review LCAN's Top Tips on Insulating.  Better, attend an LCAN B4UBuy workshop.

Start by Checking for Radon

Before insulating your home or business, it's important to check for Radon --- an odorless, colorless gas, considered the #2 cause of lung cancer (behind only tobacco smoke).  High levels of soil-borne Radon exist naturally parts of Central Kentucky, including much of the Metro Louisville.  If you have a basement, there's a risk that Radon is infiltrating into it.  Insulating can increase concentrations, which is of special concern if you spend much time there. 


If you live in Metro Louisville, request a free test kit (outside Louisville, click here).  If it tests high enough to require action, click the "Consumer's Guide to Radon Mitigation" for detailed information on how to mitigate radon before you insulate.


Work Incrementally

Unless the building was built of an especially modern material, like stress skins, structural insulated panels (SIPs) or insulated concrete forms (ICFs), focus on blocking the building's stack effect -- the natural flow of air from warm to cool --- within a leaky building envelope.

After weatherizing around doors and windows, begin by sealing the attic and perimeter rim joists, where they intersect the foundation (see photo), to block the stack effect through the walls. 


Then, if the building still is too leaky, consider insulating the walls, because they usually require messy and costly demolition and restoration.  That said, if doing new construction or large-scale renovations of existing construction, there's no better time to insulate the attic, rim boards and walls. 

Perimeter, rim joists sit atop the foundation and commonly leak if not insulated properly.

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Insulation Materials

There are many types of insulation.  Choosing among them depends on various factors, including how the building was constructed, available headroom, costs and whether you prefer a DIY product.  The products most commonly used in our area are described, below.  Learn more.

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Spray foam insulation can be applied on the attic floor or, better, the underside of the roof, which allows you to eliminate ridge and, often, soffit vents.  At usual depths, this product blocks the flow of air, letting you control indoor humidity.  You'll need many fewer inches of material compared to traditional materials.  Performance standards apply to this type of material.

NOTE:  Unless you're planning to cover it with 5/8" thick drywall, it's VERY important to choose a product without cyanurate compounds.  You'll pay more for it, but avoid the cost of an ignition-suppression coating.


Fiberglas comes in batts, as shown, or loose fill.  It usually is made partly of old glass bottles and jars, which closes the recycling loop. 


Follow prescriptive R-value codes for this product.  It's suitable for a DIY project, but take care to keep particles off your skin and out of your nose, eyes or mouth.  Avoid compressing Fiberglas batts into spaces narrower than the batt; instead, cut the batt to fit the space without having to squish it.

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Cellulose is a loose fill product and blown onto attic floors and into walls. It's usually made of recycled newspapers, treated with boric acid as a flame retardant. 

Follow prescriptive R-value codes for this product.  It can be a DIY project, but take care to keep the dust out of your nose, eyes and mouth. 

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Rigid Polystyrene (Styrofoam), which also comes in blue, white and green, can be a DIY project.  Using special fasteners or adhesive, PS works  especially well against foundations, on the insides of rim boards and beneath the undersides of floors.  Note: Extruded PS is more efficient and is trimmed with less mess than is beaded PS.

Depending on the situation, you may be able to use thicker PS sheets or layer 2-3 thinner sheets, for better insulation.  Some PS boards have tongue-and-groove edges; if what's available to you doesn't, seal the perimeter of each sheet with caulk or, for wider gaps, canned spray foam. 

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