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Unvented attic — New roof, exploring options

carpenike | Posted in Energy Efficiency and Durability on

Hi everyone,

We’re in the process of getting our roof replaced on our 1964 single floor “rancher”. The house currently has no venting at all in the attic and we’re getting mixed responses from different vendors on whether we need ventilation or not. Read plenty of things online about the negative pressures that are typically created when using powered fans in the attic and would prefer to avoid them. Another installer recommended smart vents installed under the shingles and a new ridge vent.

The only real reason we’re exploring ventilation is that the living area gets very warm during the summer. The previous home owners installed skylights which do not help things — we are removing those when the roof is redone. The attic appears to have sufficient insulation based on the home inspectors comments and a recent check by our HVAC technician. It’s all batting (I think that’s the right term) insulation.

The majority of the HVAC is in the basement. There’s a few vents that are sent from the basement to the attic as well as one return.

Should I explore venting my attic or leaving it alone and explore other options to seal the living area?

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Replies

  1. user-2310254 | | #1

    If you are doing a new roof, it is the perfect time to consider installing outside insulation. See this article for more information: https://www.greenbuildingadvisor.com/articles/dept/musings/how-install-rigid-foam-top-roof-sheathing.

    Also respond and tell us where you are located since climate matters, and whether any of your roof assemble includes cathedral ceilings.

  2. carpenike | | #2

    No cathedral ceilings. I'm in Maryland.

  3. GBA Editor
    Martin Holladay | | #3

    Ryan,
    If your attic seems dry, and there are no signs of moisture problems, then there really is no need to worry about ventilation. That said, it may make sense to install a ridge vent, especially if you intend to sell your house in the future -- some building inspectors think ventilation matters.

    You shouldn't be under the illusion that adding attic ventilation will lower your attic temperatures. It won't.

    For more information on these issues, see All About Attic Venting.

    Evidently, your complaint is that your house is hot. That raises several questions:

    1. Does your house have air conditioning?

    2. Does your house have unshaded west-facing windows?

    3. How thick is the insulation on your attic floor?

    It's certainly possible that the attic ductwork is contributing to the problem. For more information on attic ductwork, see Keeping Ducts Indoors.

  4. carpenike | | #4

    Hi Martin,

    Thank you for the response! This house isn't our long-term house so I'm hesitant to spend too much money on things that won't provide value or contribute to a quicker sale. Looking to move in around 5 years.

    The roofer was hesitant on the ridge venting as we have closed soffits. He'd rather put vents on the sides of the house and then a fan on the back.

    1. We do have air conditioning. The system checked out fine yesterday by the HVAC technician but it runs all day. I have an Ecobee thermostat that sends me notifications like, the system has been running for the last 4 hours on cold but the home temperature has increased 4 degrees.
    2. This may be our bigger problem. There's no west facing windows but we have an uncovered deck that faces south with 3 sliding doors on it. Additionally there are 4 skylights in the house. I'm thinking if I remove the 4 skylights and add cantilevered umbrellas to the deck it may solve the problem as well.
    3. The insulation is roughly a foot thick in most places in the attic.

    Thanks!

  5. user-2310254 | | #5

    Ryan. Six inches of fiberglass batt insulation might be about R-19. I believe the current code minimum for your climate is R-49. That could have something to do with your air conditioning running for hours at a time and not cooling. You might want to add insulation and also air seal your attic. Martin has a good article here on the second topic here: https://www.greenbuildingadvisor.com/blogs/dept/musings/air-sealing-attic.

  6. GBA Editor
    Martin Holladay | | #6

    Ryan,
    It's hard to diagnose problems over the internet, but your biggest problems are probably the skylights, the large areas of south-facing glass, and the ducts located in an unconditioned attic.

  7. carpenike | | #7

    Thanks everyone!

  8. charlie_sullivan | | #8

    If you are reluctant to make long term investments, I think that you still have some options that are likely to pay back within 5 years:

    -Air seal the attic floor, especially if you do that yourself.
    -Shade the sliding doors.
    -Seal and insulate the ducts in the attic if they aren't, or aren't done well.
    -Get rid of the skylights if that fits in the roofing project without a major extra cost.
    -Possibly blow 3-4" of cellulose over the top of your existing insulation, because that will improve the performance of the fiberglass as well as adding its own R-value, so you get double benefit from it, even though your existing insulation isn't too far below code. (Exposed fiberglass performs below its rating.)

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