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.

Don't be this guy!

Attend an LCAN B4UBuy workshop.  At minimum, review LCAN's Top Tips on Insulating.

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.

Insulation Materials

There are many types of insulation.  Choosing which one to use depends on various factors, including how the building was constructed, available headroom, costs and whether you prefer a DIY product.  The most commonly used products in our area are, in order of preference, spray foam, cellulose and Fiberglas.  Learn more.

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 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.

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.  This product is suitable for a DIY project, but take care to keep the dust out of your nose, eyes and mouth. 

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. 

© 14 June 2021

by Louisville Climate Action Network


PO Box 4594

Louisville KY, 40204

502.451.COOL (2665)

Monday--Friday, 9am--6pm


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