mobile home ventilation

john smith
2/27/2013
Good Day! I am installing a metal roof (over existing shingles) on a doublewide home located in Florida. I am going with the standard 1x4 batten boards with bubble foil on top of the shingles. The attic is NOT VENTED, and I am trying to lower a/c costs as we spend more money in Florida trying to keep the heat out. My question is whether to cut air passageways through the existing roof peak shingles. I had one roofer tell me that it would let the hot attic air escape out. ( underneath the new metal ridge). I am somewhat concerned about condensation issues. Any advice on this or other unforseen issues with this type of installation ?. I would appreciated any comments or advice , and I thank you all for your time and your knowledge.
Todd Miller
Isaiah Industries, Inc.
2/27/2013
By doing this, would you actually be opening up an airspace or just a fully insulated cavity? If only a fully insulated cavity then I would be concerned that opening it up really will not help matters.
john smith
3/2/2013
The attic cavity is insulated. Let's see if I can explain this a little better. The two halves of a double wide mobile homes are joined together down the center and this is referred to as the marriage wall. The mobile home installers usually lag bolt the floor joists together at the bottom of the m/wall. The top of the wall (where the trusses and the attic are located) are usually not connected and allowed to “float”. There is usually a small space between the two wall halves in the attic area. The theory is that the hot air from the attic cavity rises up through this space to the ridge shingles. Air passages are then cut through the shingles....this air rises up through the shingle cut to the new metal ridge cap and is then vented to the outside. I guess it's supposed to help lower attic temps and help with a/c costs. I hope this explains it a little better Todd and I thank you for your reply. I apologize for not responding sooner, but my IP address was blacklisted as spam and I have been trying to resolve this issue.
Todd Miller
Isaiah Industries, Inc.
3/2/2013
In this case then I think you should include a ridge vent on the metal roof, and cut air passages through the old shingles.
john smith
3/2/2013
thanks for your expertise Todd, I also forgot to ask.... do you think I should cut gable vents for the small mobile home attic, as it has no vents ?
Todd Miller
Isaiah Industries, Inc.
3/4/2013
I am not entirely sure what's going on as far as airflow with this center gap but my concern with gable vents is that they will disrupt / change airflow patterns, and probably not in a good way.
john smith
3/4/2013
I guess I am concerned that the attic has no air intakes... like soffit vents or gable vents in a traditional roof. Oh well....I guess that some air will migrate up through the nooks & crannies. thanks again for all your help Todd

1/7/2019

hey Tod, my question is i have a single 16 wide mobile home with a 3/12 pitch roof. i'm striping my roof with 1x4's and am having a metal roof installed over my existing shingles. would it be wise to rip all the way down the ridge a 1'' opening on each side of the ridge and blanket the ridge opening with a roll of attic mesh roll insulation called gaf cobra pro series attic ventilation before installing ridge cap,also would be installing a cv3 ridge rib vent inclosure on each side of ridge cap.attic has little insulation. would this help with heating and cooling or would this method cause condensation and mold issues. thanks for all your help. RD

Eric Novotny
An informed customer is the Best Customer!
1/7/2019

Where is your intake air for the ridge vent coming from?

If you strip the roof (purlins), you won't have any intake ventilation in this case.

Todd Miller
Isaiah Industries, Inc.
1/7/2019

Exhaust vents on a roof need someplace to pull intake air from. If there are no intake vents at the bottom of the roof, then there are risks with putting in a ridge vent. One side of the ridge vent may start to draw air in, which is bad because it can bring in bad weather, especially when the roof is fairly low pitch to boot. Putting the roof on battens will be helpful. It creates a good thermal break. You could, for extra efficiency, install vertical battens first along the rafters and then your horizontal battens. This creates vertically oriented air chambers beneath the roof which can then be vented with intake at the bottom and exhaust at the ridge.


1/8/2019

hey Tod, my question is i have a single 16 wide mobile home with a 3/12 pitch roof. i'm striping my roof with 1x4's and am having a metal roof installed over my existing shingles. would it be wise to rip all the way down the ridge a 1'' opening on each side of the ridge and blanket the ridge opening with a roll of attic mesh roll insulation called gaf cobra pro series attic ventilation before installing ridge cap,also would be installing a cv3 ridge rib vent inclosure on each side of ridge cap.attic has little insulation. would this help with heating and cooling or would this method cause condensation and mold issues. thanks for all your help. RD thanks TOD and ERIC my trailer has about a 6'' overhangthats soffit vented.

Todd Miller
Isaiah Industries, Inc.
1/8/2019

If the intake vents are working and air is flowing through the attic, then installing a ridge vent is fine. Make sure that the product you choose is installed appropriately and approved for 3:12 roof pitch.


1/8/2019

thanks Tod, i have about a 4-6'' soffit all the way around the trailer.pulled off 4 attic vents about 12''x12'' openings off along the roof by the ridge. Will be covering the openings with galvanized mesh wire so it can breath. Is this enough ventilation to not install a ridge vent?Appreciate your thoughts, thanks! RD

Eric Novotny
An informed customer is the Best Customer!
1/8/2019

If the soffits are continuous around the perimeter and are open, so should the ridge. The ventilation should be continuous and in balance with the ridge vent.

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