6

Edit: Updated with responses

The house in question is a 2-story w/ basement, with a two-zone (ground floor, and upstairs) HVAC system in NY. There is an attic with a ladder(*) housing the upstairs blower(?) which recently needed to have its motor replaced - it had been gradually degrading and finally stopped working during a recent heat wave.

As part of the repair, it was noted that the attic is a sealed attic. I installed a temperature sensor up there and have noticed the attic space can get up to 50 Celsius for a few hours a day.

Question: Do I have a problem with heat or are "sealed attics" expected? Should I worry the heat can degrade my air-conditioning/heating unit? As the house is 20 years old, I can't imagine I am out of code here in NY.

Update(s) - Thank you everyone, a lot of surprises due to your guidance.

  1. First picture show the insulation appears to be above the rooms, versus on the roof.
  2. I've also attached a graph showing the temperature.
  3. I've also looked at the new motor and confirmed the ambient temperature specification at 40degrees (in addition, it appears I've been scammed. The motor quoted pre-installation for $1000+, versus what was actually installed is on Amazon for $100 new... will start a new thread to dig into if I've actually been scammed.)

Air Conditioning Unit

Temperature comparison showing Attic as outlier on hot days

8
  • 2
    How is the attic insulated? Is there insulation on the underside of the roof or just in the attic floor? How much and what kind? Jun 4, 2022 at 17:52
  • 1
    Check the blower motor specs ! 50C ambient + 30C operating temp = 80C load.
    – Traveler
    Jun 4, 2022 at 20:28
  • 1
    Vented or not vented attic. Both have they pro and con.
    – Traveler
    Jun 4, 2022 at 20:29
  • 1
    Where is the insulation in your attic located? Jun 4, 2022 at 21:44
  • Thank you for the feedback all. I will update the post shortly. It turns out, in the course of getting these updates, I have been scammed by the hvac company...
    – NJL
    Jun 5, 2022 at 2:10

4 Answers 4

7

I would say that there is no code violation as insulation and or vents have not always been required.

I would want to vent the space for multiple reasons

A hot attic reduces the roofing life on most types of roofs.

A hot attic will increase the cost of cooling

As you have found motors in hot places don’t last as long, totally enclosed fan cooled motors don’t get much cooling if the temp is actually above the operating temp.

I have used powered vents in multiple homes to reduce the heat load from the ceiling and this reduces the amount of BTU’s to cool the living space. So this along with extending the service life of the equipment it can help to vent powered or natural circulation.

2
  1. For code violation: look up the housing code for your county. It will tell you exactly what you need to know, but I've never known a code that "required" venting.
  2. In winter: an unvented attic accumulates heat and causes the attic and roof to become warmer than the outside temperature. In snowy areas, this causes the snow touching the roof to melt too fast. This leads to ice jams alongside the edge of the roof, and in gutters. These can cause extensive damage to the roof and gutters.
  3. In the heat of summer: if in a humid area, an unvented attic can cause mold growth due to low air flow, low light, and high moisture.
1
  • Note that while what you are saying applies to the OP's attic (unvented but not cathedralized), it does not apply to cathedralized/"hot roof" configurations that put the thermal and air barrier planes at the roofline instead of beneath the attic Jun 5, 2022 at 6:42
2

Your best source of information would be your local building department / inspector. Codes are not consistent from place to place. Here is some information from the US government department of energy. https://basc.pnnl.gov/code-compliance/sealing-and-insulating-existing-vented-attics-code-compliance-brief, https://basc.pnnl.gov/code-compliance/controlling-moisture-unvented-attics-code-compliance-brief. There are many arguments on whether it needs to be vented or not venting is better. Each case will be different. Obviously the cooler the attic the better for your blower but... Sorry but not knowing where you are will have a big effect on the answer to your problem.

1

You need to vent this or, better yet, convert it to a proper conditioned attic

IRC R806.1, as of now, requires attic ventilation in your situation, and any case where the rather complicated IRC unvented-attic provisions in IRC R806.5 do not apply. In warm climates, this can be accomplished using a vapor diffusion port setup provided the attic doesn't have HVAC in it and your AHJ accepts such things, as per BSI-119.

However, New York State (both NYC and upstate) gets cold enough that you have to worry about being damned by ice dams, so you also need sufficient venting to keep the roof deck from warming up and melting the snow on top. See BSI-046 for details on this.

Thing is, though, any attempt to vent your attic will have to provide enough ventilation to overpower the warm air leaks from the ceiling. And the HVAC system. And the condensate drain. As a result, you're better off retrofitting your attic to be an unvented conditioned attic, with insulation at the roofline, as per BSI-119. However, that change will require you to replace your furnace with a sealed-combustion unit, or ditch gas entirely in favor of heat-pump heat, due to the fact air leakage won't be available for combustion draft any longer.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.