When you’re looking for ways to increase the energy efficiency of your home and reduce utility costs, you’ll often see increasing the R-value of your attic insulation as a recommendation. Higher building envelope thermal efficiency translates to lower HVAC system sizing and cheaper operation costs. But what about insulating the attic over carport structures?
Shared attic space between your house and carport is unconditioned — meaning it’s not heated or cooled. Leaving the carport portion uninsulated helps prevent moisture buildup since unconditioned attics need ventilation to allow heat and humidity to escape.
How Attics Work
Attics create a buffer between outdoor conditions and the interior of your home. Hot, humid attic air flows through vents — usually intake vents at the lowest points like the eaves, and exhaust vents at the high points like the ridge. This ventilation is critical for controlling heat and moisture. Insulation installed on the attic floor keeps conditioned air from the rooms below from entering the attic. This helps improve energy efficiency and comfort. Check out the basics of attics to learn how to keep your attic in tip-top shape.
Insulating Carport Attics
Carports have at least one open side, meaning the space stays unconditioned. So, even with an open connection to the insulated main attic, the carport attic remains an unconditioned zone.
Insulating this area could cause problems like:
- Moisture, mildew, mold, or corrosion from condensation
- Wasting money to insulate an unheated, uncooled area
- Attic ventilation being blocked by insulation batts
Adding insulation to an open carport wastes money since the space isn’t climate-controlled. It can also lead to moisture issues if ventilation is restricted. Consider your climate control and ventilation plans carefully before insulating a carport attic.
What to Do
Below are some tips for maintaining a proper connection between your carport attic and the rest of your home’s attic space.
- Allow airflow between both attic spaces — don’t fully isolate the carport section.
- Add soffit vents along the edges of the carport to encourage ventilation. Soffit vents are openings that allow air to flow in along the eaves or lower roof edges.
- Caulk or spray-foam major air leaks between the house and the carport attic. This prevents conditioned air from escaping and causing condensation.
- Use unfaced insulation like fiberglass in the main attic so moisture can pass through.
- Install a dehumidifier to control moisture actively.
When to Insulate a Carport Attic
If you enclose your carport and heat/cool the space, insulate the attic floor like the main house attic. Just be sure to maintain proper ventilation. Overall, don’t insulate an open-sided carport attic. Focus on ventilation instead — a cost-effective move for homeowners.
So, Should You Insulate an Attic Over a Carport?
In most cases, no. You don’t need to insulate an attic over an open carport because it’s an unconditioned space. Insulating it could actually cause moisture and ventilation problems. Leaving it uninsulated is fine as long as the carport attic integrates with the insulated main attic for airflow. The only exception is if you enclose and climate-control the carport.
FAQs About Insulating Carport Attics
Should I insulate the floor, walls, or ceiling of my open carport?
For an open carport, leave all surfaces uninsulated and unconditioned — except do insulate any shared walls between the carport and house.
What if I enclose and climate-control my carport — insulate then?
If you fully enclose and heat/cool the carport, insulate the attic floor like your main house attic. Make sure to maintain proper attic ventilation, too.
How can I improve carport attic ventilation?
Add more soffit vents along the edges if possible. Ensure the carport attic connects openly to the main attic for airflow. You can also add exhaust vents at the roof peak.
What’s the best way to insulate the main attic adjacent to a carport attic?
For proper attic ventilation, use loose-fill fiberglass insulation — it’s unfaced, allowing moisture to pass through.
Should I weatherstrip the door between the house and the carport?
Yes, weatherstrip this door so conditioned indoor air doesn’t escape into the carport. Limiting air leaks between conditioned and unconditioned spaces is critical.
