Tips on Air Sealing Your Attic to Save Energy

Are things feeling a little drafty upstairs? If you’re a homeowner dealing with high energy bills and less than comfortable indoor climates, the answer to your problems may be just above your head. Before investing in high tech services and expensive ventilation systems, it’s essential that you properly seal your attic. Which can easily be done by contacting local insulation contractors.

From finding leaks to choosing materials, these tips will help you find the solutions for all your attic sealing needs. It’s time to cut your heating and cooling costs and finally put an end to your attic issues. Read on to discover how.

Tip #1 Have the Right Tools

Before delving into leaks and gaps, take note of what you’ll need to do the job.

For DIY air sealing, you’ll need the following tools:

  • Caulk and caulking gun
  • Hammer
  • Screwdrivers
  • Multitool
  • Utility knife
  • Coverall Suits
  • Gloves
  • Headlamp
  • Respirator mask
  • Expanding Foam

You may also need expanding foam, insulation, garbage bags, and other sealants and adhesives. Your materials depend on your leak situation.

Remember to take safety precautions when engaging in any major home project. When air sealing attic spaces, dust masks, gloves, and eye protection are essential. Stay safe.

This can be an intensive and time- consuming project, so make sure you have the bandwidth to take it on. Ultimately, it may be worthwhile to seek a professional solution. The cost to air seal attic spaces can range from the high hundreds to the low thousands depending on what’s required. 

Tip #2 Know How To Find Your Leaks

The signs of a leaky attic are hard to miss. If you’re dealing with any of the following issues, it’s likely a sign of improper attic air sealing:

  • Noticeable air drafts 
  • Inconsistent temperatures between rooms
  • Heavy dust particles
  • Increasing energy bills

While you may know you have a problem, finding the source of your attic leaks is another issue. 

Attic leaks can come from anywhere in your attic, and we’ll take you through the process of sealing each specific area, but before you can seal, you need to discover your leaks.

There are several ways to find air leaks, including:

  • Visual inspections – Conduct a thorough visual search of your attic space for potential leaks. Pay close attention to your vent stacks, ductwork, attic hatch, and joists, and note where you see gaps. Additionally, trace the envelope perimeter around your attic for any spaces in the structure.
  • Paper test – For doors and windows, this test can determine if additional sealing is required. Open your doors and windows, place a piece of paper below, then close. Now, try to pull the piece of paper out. If it tears, you have a tight seal, but if the paper slides out easily, you’ve found a potential source for air leakage.
  • Smoke test – Before conducting a smoke test, it’s essential to turn off your fans and combustible appliances, shut your doors and windows, and wait for a breezy day. After doing so, light an incense stick and move around through your attic. You’ll know you have a leak if the smoke is blown or sucked outside.
  • Light test – This test requires two people. Shine a flashlight from the interior of the attic outside and have your partner look for spots where it shines through. Additionally, you can stand in your unlit attic and look for areas on the floor where light is visible.

Tip #3 Seal Major Holes and Gaps Before the Small Ones

After assessing where your leaks are, it’s best to tackle the biggest issues first. It’s no surprise that larger holes have the propensity for letting hot air and cold air in (or out) and drastically affect your home efficiency. If you’ve ever wanted to know how to cool an attic, sealing major holes is an efficient way to keep cool air in your attic and regulate through your entire home.

Here’s where large gaps are often found:

  • At the intersection of walls and floor
  • In dropped ceiling areas
  • Under knee walls

Frequently, homeowners benefit from stuffing open stud cavities with attic insulation. This can be done in several ways, including:

  • Stuffing bags – You can cut standard fiberglass insulation into smaller pieces (each roughly 16 inches) and place them into contractor-sized trash bags.1 These stuffing bags are ideal for squeezing snuggling into the large cavities of your attic, leaving little space for air or moisture to enter.
  • Reflective foil insulation – Cover the opened frame area above your dropped ceiling with reflective insulation or a rigid foam board. Cut your material to fit snugly over the frame and use caulk, staples, or nails to connect the piece above the soffit.

Keep an eye out for dirty-looking insulation on your attic floor. Insulation can act as a kind of filter and as air and dust particles move through, some become trapped within the attic insulation. The overall purpose of insulation is to lower your heating and cooling costs, so if you’re seeing signs of dirty insulation, it may be time for a replacement. 

Tip #4 Seal Furnace Flues

The space around your chimney, furnace, or water heater flue is a point of leakage for many households, but flue sealing is more complicated than just filling holes. That’s because most building codes require at least 1 inch of clearance between metal flues and any combustible materials.1

This can put you in a tricky situation for properly sealing your attic. Fortunately, there is a way to seal up your flue.

  • Aluminum flashing – Construct an exterior shield around your flue creates a tight seal. Surround the base of the flue with custom-cut aluminum flashing, and seal the gaps where the flue and flashing meet with specialized heat-resistant caulk.1
  • Aluminum dam – After constructing the flashing, craft an aluminum dam to wrap around the flue itself. The dam will allow you to add further insulation around your flue without any insulation coming in contact with the flue. It’s a safe and effective way to strengthen your air seal.

Tip #5 Seal Areas Around Doors and Windows

Feeling a draft out of your attic window? The process of sealing attic air leaks coming from doors and windows is much different than other aspects of attic sealing. After all, you’ll still need to be able to access and open these fixtures.

Seal door and window air leakage with the following methods:

  • Wood, caulk, foam – There are a variety of materials used to properly seal windows, and the choice often comes down to the severity of the air leak and the age of the windows themselves. You may choose to use caulk or foam around the interior frame of the windows or opt to remove and replace wood panels that have been damaged.
  • Weatherstrip  – Apply adhesive foam weatherstrip tape around the perimeter of your attic hatch doors. This should tighten the seal while the door is shut. Additionally, consider attaching fasteners to help pull the door tightly against the weather stripping for an improved effect.2

Be careful of lead dust when dealing with older painted windows. A tight seal around your doors and windows is great, but nothing’s more valuable than your health. Take precautions and talk to an expert if you’re unsure of the potential risks.

Tip #6 Seal Ducts 

You’re on double duty with duct sealing. Both the holes where your ducts enter your attic and the ducts themselves should be sealed. Feel along the edges of the duct while your HVAC system is on to determine whether your ducts are leaking.

If you notice unwanted airflow, try these tips for sealing your ducts:

  • Mastic foil tape – Wrap specialized duct sealant around the leaking area and ensure a tight seal. While you may be inclined to pick up a normal roll of duct tape, it won’t hold up, and soon you’ll be dealing with the same problem all over again.
  • Insulation on top – After sealing your ducts, professionals recommend properly insulating them as well. Not only will the insulation assist with your overall energy efficiency, but high-quality foam spray can protect your ducts against possible attic air leaks for years to come.

Duct sealing can be difficult. Stepping over studs, searching for leaks, and diligently wrapping with duct sealant can be an exhaustive process, but all that work is worth it when you receive a significantly smaller utility bill.

Tip #7 Save Small Holes for Last

Before completing your air sealing project, double-check for smaller holes you have yet to plug. Expanding foam and caulk are your best options for a quick fix to your smaller attic gaps.

Pay special attention to areas like:

  • Attic bypasses – Beneath your insulation, the attic electrical bypasses may transfer airflow from your living area to the attic. Lift your insulation and seal the bypass areas with a caulk to plug up any holes.
  • Plumbing pipes – Don’t mistake these pipes for ventilation ducts or your flue. Plumbing pipes are typically made from PVC and don’t need specialized insulation, simply spray expanding foam or caulk into the gaps surrounding the pipe’s entrance and call it a day

Attic Construction: For All Your Attic Sealing Needs

Leaks aren’t easy, and plugging holes to control your hot air and cold air efficiency isn’t as simple as it sounds. Scrounging through the attic with a headlamp and a handful of insulation could lead to a tighter seal, but it could also be an ineffective, drawn-out process if you don’t have the time or resources. If you’d prefer to take the professional route and ensure a job well done, Attic Construction is your solution. 

For us, it’s not just about sealing but protecting your attic for the long haul. We offer services like pest-proofing, insulating, and attic cleaning in Orange County, San Diego, or Phoenix. All of our work comes with a 1-year warranty, and we take pictures of your attic to show you exactly where the project starts and where it ends. At Attic Construction, we’re interested in transparency, efficiency, and sustainability. If you’re ready to seal, contact us today.



  1. Energy Star. A Do-It-Yourself Guide to Sealing and Insulating With Energy Star. 
  2. Energy Star. Sealing Behind Window & Door Trim Project. 
  3. Energy Star. What to Look For: DIY Checks and Inspections. 

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