Building Insulation: Where it is Needed and Why It's Important

Did you ever notice your AC or heater constantly turning on during the extreme temperature months? If your A/C or heater takes a long time to cool or warm or you notice high utility bills, lack of good insulation or worn out insulation might be the culprit. It’s a problem when your house is leaking air.

Having air leaks means your building envelope might not be “enveloping” the building as it should. 

The building envelope, which comprises building structures (windows, walls, and doors) and insulation, acts as the barrier between the conditioned and unconditioned parts of your building. 

Building structures act as the first barrier against the weather and outdoor temperature. But even then, heat or cold transfers through the walls and ceilings through the tiny gaps in different areas of the building.

Insulation is the protective sheath that prevents the temperature outside from affecting your living space. Proper insulation makes your home comfortable, free from drafts, and it saves you money on cooling/heating bills. 

But even if you have sound insulation, air leaks can still cause you to spend money on energy bills more than you have to. Addressing the gaps before insulating is the first step towards an effective building envelope.           

Areas where there are common air leaks

Gaps are commonly found where two different building materials connect (e.g. outdoor faucets, and in-between chimneys and sidings).


Common air leaks are found in:

  • Attic hatches

You can use self-sticking weatherstrip or compression bulb weatherstrip.

  • Door, window frames and kitchen exhaust fans

Seal with caulk sealants or foam/rubber gaskets.

  • Chimney and flues

For heating elements like these, you can use RTV (Room Temperature Vulcanizing) silicone which cures at room temperature.

  • Electrical outlets, light switches, plumbing

Use one-component foam sprays.

  • Recessed lights 

Put can light covers on recessed lights that don’t have an IC (insulation contact) rating.

  • Rim joists 

Caulking or foam sprays are used for sealing in joists 

Testing for air leaks

A blower door test is commonly done to test for air leaks when you book for an energy audit for your home.

Another way to check for air leaks on your own is by doing a building pressurization test. 

On a breezy day, turn off your furnaces, stoves, and other combustion appliances. Turn on all exhaust fans to drive air outside and shut off all windows and doors.Dampen your hand and direct it to places where you suspect an air leak. If your hand is cooled, then there are gaps that need sealing. 

Where to Insulate and Why  

Once all gaps have been sealed, insulating further protects and shields your home. 


Of all the places to be insulated, the attic should be the first in the list. This area receives the most heat from the sun. Through convection and radiation, the heat transfers through the roof, moves to the ceiling joists and creates thermal bridging to the living space.

Improper insulation in the attic or lack thereof can lead to condensation which causes mold growth and damage on both wood and metal attic structures. And in the winter, the heat from the living space rises in the roof and produces ice dams which damage roof shingles in the long run.

The areas that need attic insulation are attic access doors, wall studs, attic rafters, and ceiling joists.   

Solution: batts, blown-in and spray foam insulation

Cathedral ceilings 

Keep the ceiling temperature even with the room temperature to prevent condensation and decay of wood structures.


  • Unvented cathedral ceilings or “hot roofs”

Unvented cathedral ceilings need to be moisture-free to avoid roof sheathing from deteriorating. Closed-cell spray foam insulation doubles as a vapor barrier and insulation.

  • Vented cathedral ceilings

For vented cathedral ceilings, open-cell spray foam is a great choice. If you want a less costly alternative, you can opt for batts insulation.    


Heat from outside is conducted through walls. To minimize the heat transfer from outside and in-between rooms, insulate your walls for thermal protection. This way, moisture and condensation risks are eliminated.

Exterior walls

Blown-in (dense-pack) insulation is the most recommended type of insulation for exterior walls. It can be added without causing disturbance to the other structures. Holes are drilled on the exterior and a blower is injected in these holes, filling the wall cavities and sealing air gaps.

Interior walls 

For existing interior walls, blown-in (dense-pack insulation) can also be installed without tearing the drywalls. For exposed drywalls, batts and spray foam insulation are good choices.  Open-cell and closed-cell spray foam can help reduce noise.

Basement and crawl spaces

Improve indoor comfort by insulating your basement. It also prevents condensation, mold growth and pest infestation.

  • Conditioned basements 

Insulation on the basement can be done on either walls or on basement ceilings. Wall insulation is typically recommended for conditioned basements with almost the same temperature for the living space.

In existing homes, interior insulation is done. Fire-rated covers for insulation materials are used to prevent any gas leaks. And to prevent moisture from reaching insulation, vapor diffusion retarders are set depending on the perm rating.

Places in Zone 2 like Houston are recommended to use Class II vapor retarders (3” open-cell SPF, kraft-facing on batts, and >1” thick extruded polystyrene) and Class III vapor retarders (latex paint, plywood, and  #30 building paper)

If your home is still under construction, insulation is installed on exterior walls. It saves basement space (compared to interior insulation) and keeps interior walls free from moisture

  • Unconditioned basements

If you have unconditioned space and you don’t want heat from the above floor exchanging with the air in the basement, go for ceiling insulation.

  • Crawl spaces

For unventilated crawl spaces, insulation is recommended on foundation walls. This way, temperature from the conditioned living space reaches pipes and ductwork and protects them from freezing. To keep the crawl space and insulation free from pests, the area should be airtight prior to insulation.

Solution: batts, blown-in, and spray foam insulation 



Having proper building insulation reduces the stress on your mechanical systems.This results in lower energy bills. Your building will last longer and you live in a comfortable draft-free home.  Koala Insulation of Northwest Houston can help you choose the best insulation tailored for your needs. What are you waiting for-- book your free insulation evaluation with us today!


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We Provide Insulation Services to the Following Northwest Houston Areas

Houston, Spring Branch, Jersey Village, Willow Brook, Copperfield, Cypress, Mason Park, and Cinco Ranch

Counties Served

Harris County, Waller County, & Fort Bend County

Zip Code

77040, 77041, 77080, 77043, 77055, 77070, 77069, 77066, 77065, 77449, 77450, 77433, 77429, 77095, 77084, 77064

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