Roof ventilation (or lack there of)

Specific Inspection Topics Exterior Inspections
1

House built in ‘71. Gable & Hip roof. 2’ wooden soffits around the perimeter of home. There were only roof vents. No gable or soffit vents whatsoever. Attic looked great with no history/signs of trapped moisture whatsoever (plywood sheathing/ 2 x 6 rafters, built well). The insulation was 12 or so inches of loose fill cellulose. Electric ceiling heat.

Can someone please try and enlighted me on why there’s no soffit or additional vents to work with roof vents?

I’ve seen plenty of attics with obvious ventilation concerns, but I am a bit curious about this. Would you suggest additional ventilation?

Any help/insight is always appreciated!

2

I have 2 houses that are similarly vented. Dry as a bone and no problems in a sub tropical climate. That type of roof venting was very common down here.

3

I agree with John.

4

With asphalt shingles?

Anyone up north?

5

I admit I have seen homes with lack of ventilation that had no damage and would like to know myself.

My first thought is life of shingles is reduced form over heating in the summer.

It is still recommended.

6

Was there a vapor barrier under the insulation?

7

Ventilation means air movement, what happens when air moves ???

8

No VB.

9

The ceiling electric heat is a factor. That is your thermal barrier and will produce sufficient “ventilation” as well as a lack of humidity loss through the ceiling.

Hope this helps;

10

Insulating exterior wall top plate from attic

This is from the site Kevin recommended in another thread.

11

If you see a house that’s almost 40 years old and has no problem in the area in which you have a question… it’s been working well for a long time… don’t recommend changes.

12

“That is your thermal barrier”

Wouldn’t the thermal barrier be the 12" of cellulose and any airsealing done on the ceiling beneath the insulation?

will produce sufficient “ventilation”

How does does the radiant electric heat in the ceiling produce ventilation?

“a lack of humidity loss through the ceiling.”

How does does the radiant electric heat in the ceiling reduce humidity transfer through the ceiling?

13

This house with electric radiant ceiling heat may benefit from the addition of more cellulose depending on the electric rates for the area.

Radiant heat panels operate at 95-100 deg F which raises the Delta T (temperature difference from indoors to outdoors) which drives heat to the exterior. We usually use 68-72 deg F as the indoor temp when calculating heat loss from a building when determining HVAC heating equipment size and individual room heat needs at design temps. The Delta T is now raised by about 30 degrees!!

An economic analyses of heat $$ saved by the extra insulation versus the cost of the extra insulation should be done before adding any insulation. If the payback is within 6-10 years, its a pretty good deal.

14

Originally Posted by wdecker http://nachi.cachefly.net/forum/images/2006/buttons/viewpost.gif
*"The ceiling electric heat is a factor. That is your thermal barrier and will produce sufficient “ventilation” as well as a lack of humidity loss through the ceiling.

Hope this helps;"*

BUMP!!!

15

[quote=Brian A. MacNeish;623165

Originally Posted by wdecker [http://nachi.cachefly.net/forum/images/2006/buttons/viewpost.gif]
(http://www.nachi.org/forum/f16/roof-ventilation-lack-there-47793/#post619040)
“The ceiling electric heat is a factor. That is your thermal barrier and will produce sufficient “ventilation” as well as a lack of humidity loss through the ceiling.”

]“That is your thermal barrier”

Wouldn’t the thermal barrier be the 12" of cellulose and any airsealing done on the ceiling beneath the insulation?

will produce sufficient “ventilation”

How does does the radiant electric heat in the ceiling produce ventilation?

“a lack of humidity loss through the ceiling.”

How does does the radiant electric heat in the ceiling reduce humidity transfer through the ceiling?
[/quote]

BUMP