Roof Renovation Questions/Recommendations?

12 years ago

I have a 1970s era two-story (big rectangle) home with the original asphalt shingles in place. It is a hip roof and has adequate soffit inlets but very poor peak (output) venting. radiant heat is a pretty big issue and is contributing to comfort issues in the upstairs rooms. I've considered encapsulating the entire space with closed cell SPF but it's prohibitively expensive. I would like to re-shingle, add ridge venting, and provide a continuous radiant barrier on the under side the the rafter-bays as less expensive and more traditional alternative. Here's the questions:

1) As it's a hip construction, how does one allow for airflow where hip raters and jack rafters meet (where the cavity ends before the roofline? Holes drilled? Notching?

2) Continuous foil sheeting seems to be the most cost effective radiant barrier, but I'd like a rigid baffle for the ventilation channel, too. 1/2" foil-faced polyiso sheets fastened continuously to the inside rafter edge seem to fit the bill, but is there an easier/faster/cheaper way that would still perform both purposes?

3) when I install the radiant barrier, most recommendations include leaving a gap between it and the insulation on the attic floor. Is this to prevent contact (and transmission of stored heat) between the barrier and the insulation? Wouldn't this allow for free airflow near the soffit, decreasing the effectiveness far more than it would transmit heat to the floor joist materials?

Hopefully, I can bring the ambient temps in the attic down to manageable levels so I can consider using the space for ducting new HVAC gear...hopefully.

Thanks,
Dan

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Seabornman

4 days ago

@millworkman these are AI generated posts. All about drumming up business.

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Comments (8)

User
12 years ago
Your descriptions are not clear and you haven't even told us the climate.

Why can't the eave and ridge vents work if the attic is open? Do you plan to insulate the rafters?

What gap are you asking about? Where is the soffit?

Will the radiant barrier be on the attic floor or the rafters?
dgeist
Original Author
12 years ago
Sorry, I'll try to clarify:
- Atlanta, Georgia (near the top of zone 3, I believe)

- The eave and ridge vents CAN work (I am supposing) but my concern is airflow in the rafter cavities which are between the hip rafters and jack rafters (probably 1/3 of the rafters). They meet at an angle part of the way up the roof (not all at the peak as in a gable roof). I would like to know if I need to facilitate some kind of path for the air at those very spots.

- As I said, I do not want to spray the rafters due to it being cost-prohibitive.

- As I said, I want to put a continuous radiant barrier across the underside of the rafters (not on the deck, not on the floor).

- The gap is the recommended one I have seen in various sites between the bottom edge of a continuous radiant barrier and the floor-located insulation. I don't understand the purpose and was hoping someone could advise.

Thanks.
Dan

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User
12 years ago
''Prohibitively expensive'' is all of the monthly extra expense for a couple of years that you will be saving up front. Pay now, or pay later. The best choice for your climate and roof situation is an unvented attic with the insulation placed at the roof deck. Get more quotes.
millworkman
4 days ago
" Atlanta contractor perspective here "

@Edward Harry 12 year old post, times, mnaterials and trands are all different as someone in business should know. Reading is fundamental.
PRO
Mark Bischak, Architect
4 days ago
At this point, they could be replacing the roof shingles again.
dgeist
Original Author
4 days ago
last modified: 4 days ago
Funny you should mention it. I did end up getting 6" of closed-cell foam in the space and GAF timberline architctural shingles. We also moved all the upstairs ducting into the attic space with a dual-fuel heat pump and have had excellent climate comfort. I've been very happy with both for over a decade and the roof is still going strong, although my kids running super-long showers and some leaky framing around their bathroom has introduced an unplanned moisture load so dehumidification is definitely necessary in the attic. Utility bills have been low so long I forgot how much higher they were just after buying the house.
PRO
Mark Bischak, Architect
4 days ago
"Utility bills have been low"

Music to my ears.