Thread: No soffit venting

Inspected a log home yesterday with a saltbox roof. Structure has only a ridge vent that is visible only from the exterior and can not be verified as there is no attic or attic access. Even though there is no attic, should not the space between the roof and the ceiling be vented and should not soffit vents be utilized to assist the ridge vent for proper ventilation.

I stated that the ridge vent is only visible from the exterior as I have several contractor friends that have installed these for clients for the sole purpose of appearance only and that do not function as a vent. I have also seen this in prior inspections.

Thank you in advance,
Sid

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Here is the NC code for what you described:

R806.1 Ventilation required. Enclosed attics and enclosed
rafter spaces formed where ceilings are applied directly to the
underside of roof rafters shall have cross ventilation for each
separate space by ventilating openings protected against the
entrance of rain or snow. Ventilating openings shall be provided
with corrosion-resistant wire mesh, with 1/8 inch (3.2
mm) minimum to 1/4 inch (6 mm) maximum openings.

R806.2 Minimum area. The total net free ventilating area
shall not be less than 1/150 of the area of the space ventilated
except that reduction of the total area to 1/300 is permitted, provided
that at least 50 percent and not more than 80 percent of
the required ventilating area is provided by ventilators located
in the upper portion of the space to be ventilated at least 3 feet
(914 mm) above the eave or cornice vents with the balance of
the required ventilation provided by eave or cornice vents. As
an alternative, the net free cross-ventilation area may be
reduced to 1/300 when a vapor barrier having a transmission rate
not exceeding 1 perm (5.7 x 10-11 kg/s . m2 . Pa) is installed on the warm-in-winter side of the ceiling.

Exceptions:
1:. Enclosed attic/rafter spaces requIrIng less than 1
square foot (Q Q929 mZ) of ventilation may he vented
with continuous soffit ventilation only
2: Enclosed attic/rafter spaces over unconditioned space

may he vented with continuous soffit vent only

The attic should be made accessible. The IRC states that any attic space of 36 sq. ft. or more shall be accessible. Of course proper and adequate ventilation is required.

Darrell

Darrell,

There is no attic. Many mountain homes in this area have cathedral roofs with no attic or attic access.

Sid

Originally Posted by sidney alstad

Inspected a log home yesterday with a saltbox roof. Structure has only a ridge vent that is visible only from the exterior and can not be verified as there is no attic or attic access. Even though there is no attic, should not the space between the roof and the ceiling be vented and should not soffit vents be utilized to assist the ridge vent for proper ventilation.

I stated that the ridge vent is only visible from the exterior as I have several contractor friends that have installed these for clients for the sole purpose of appearance only and that do not function as a vent. I have also seen this in prior inspections.

Thank you in advance,
Sid

It is best to have continuous ridge vent and continuous soffit vent.

The insulation in the bays should have a baffle above them but even if it is already built and you add the ridge and soffit vent you are going to move heated air and moisture out just not as good as with baffles. I have see many hmes with the finish peeling off the drywall because of locked in heat and moisture. on cathedral ceilings.

Unless of course you have structural insulated panels.

whoops: good reading skills by darrell
darrell

There is a school of thought which believes that ridge vents alone supply adequate ventilation. I personally do not see physics operating that way. The attic, or in this case the enclosed rafter spaces, is cooled by a convection current - think: heat rises. With no intake, i.e. the soffit vents mentioned by Mr. Menelly, there can be no convection current, and thus no proper ventilation. Just my opinion.

If the lack of soffit vents are giving you heartburn then you should tell your client that the home does not have soffit vents.

Can soffit vents be properly added and made functional if the home does not have an attic? If not, then I would not recommend them.

Originally Posted by Scott Patterson

If the lack of soffit vents are giving you heartburn then you should tell your client that the home does not have soffit vents.

Can soffit vents be properly added and made functional if the home does not have an attic? If not, then I would not recommend them.

It seems that your comments are directed to the OP, but just to be clear, I was not advocating recommending installing soffit vents in the home described at this late date, only noting that they should be there. Just my opinion.

A standard soffit type vent would probably serve no purpose as this home does not have an attic space. There are a couple of options listed on the following website home building technical information resources builders construction remodeling innovations (roof section). Using one of these products, along with baffles or some other system to allow air flow seems to be the best option for a home with out an attic.
I have seen the same type of set up you are describing on some homes in my area as well. Eventually the lack of ventilation does become an issue (premature roof covering wear, etc).

Could be a non vented roof assembly, insulated with foam.

There are two possible roof methods that could be installed here,

The first being a sips panel made up of a #8 pd felt with the foam and OSB or plywood fastened to the rafters or purlin system. this would have the shingles direct applied to the sheating end of the SIP's panel. Maybe the cavity created caused the builder to add the ridge vent. I am not a big fan of the SIP's used on the roof because the shingles are direct applied to the panel and there is no air space underneath.

The next which is the most common, we call it a cold roof system is the foam insulation is installed over the T&G pine ceiling with a layer of #15 felt in between. there are sleepers fastened in the direction rafters would be through the entire system into the exposed rafter or purlins with RXR spikes and then the roof is sheathed giving an space in between the roof insulation and the roof sheathing. This system can recieve the ridge vent and usually a 2" or 3" round vent drilled at the soffit. I have installed strip vents at the soffit, it was too labor intense with the framing.

With a ladder you can see at the roof edge what system is installed. Some times there are no soffit vents installed from pure laziness but in my opinion, this system is the best for big timber and log buildings

Originally Posted by Elliot Franson

There is a school of thought which believes that ridge vents alone supply adequate ventilation. I personally do not see physics operating that way. The attic, or in this case the enclosed rafter spaces, is cooled by a convection current - think: heat rises. With no intake, i.e. the soffit vents mentioned by Mr. Menelly, there can be no convection current, and thus no proper ventilation. Just my opinion.

I agree with you; the basic physics require an air inlet to support an outlet. Otherwise you won't have ventilation and may even draw cool air from inside the home through any openings (e.g., electrical, etc.).

Originally Posted by Eric Gulotta

Could be a non vented roof assembly, insulated with foam.

Or dense pack cellulose would not require a vapor barrier because it is not air permeable.
There are many Paints and Paint Primers that will meet the requirement of a vapor barrier and no ventilation would be required.
If this is T&G (not a painted surface) there may have been a plastic vapor barrier installed. More than likely an inspection(or) would not be able to determine if there is any problem for moisture build-up within the cavity....except if there is visual evidence of damage.

In a situation where there is no continual open attic space between rafters...(IMO) it would be better to stop the moist air from ever entering the insulated space (assuming a permeable insulation like fiberglass) because the moisture is going to condense (dew point) and/or freeze somewhere in the insulation and not necessarily where ventilation is going to do any good.

We need more info to make any kind of a recommendation. We need to see how the ceiling was put up and what type of insulation.
Even if it is exposed rafters with exposed wood ceiling, there may still be rafter cavities above, which can benefit from soffit venting. Especially if it's ordinary batt insulation, there will be an air gap above, between the insulation and the cold undersurface of the roof deck.

We used to see a lot of T+G cedar plank ceilings in the 70's. They had minimal insulation sometimes but usually there would be strapping and cedar shakes or shingles, self-venting roofs.

Originally Posted by Larry Morrison

Or dense pack cellulose would not require a vapor barrier because it is not air permeable.
There are many Paints and Paint Primers that will meet the requirement of a vapor barrier and no ventilation would be required.
If this is T&G (not a painted surface) there may have been a plastic vapor barrier installed. More than likely an inspection(or) would not be able to determine if there is any problem for moisture build-up within the cavity....except if there is visual evidence of damage.

In a situation where there is no continual open attic space between rafters...(IMO) it would be better to stop the moist air from ever entering the insulated space (assuming a permeable insulation like fiberglass) because the moisture is going to condense (dew point) and/or freeze somewhere in the insulation and not necessarily where ventilation is going to do any good.

The moisture already gets in...thru the drywall on its normal migration to the exterior. If not vented it will create all and then some of the problems listed above. Of course this depends on the climate as well so to the area in question one would have to know the normal cycle of whether, humidity, freezing, vapor barriers applied or not. In any case...like any attic...there will already be and continue to be heat and moisture. It needs to be vented out.

I did mention structural insulated panels and such above. If there is a loose fill cavity and not solid foam it is better to vent it.

This may be a climate controlled attic space that has no gable or soffit vents. A builder in Las Vegas installs one roof vent that connects to the air return for fresh air ventilation. The blown in insulation is contained in a net which is attached to the trusses directly below the sheathing. The temperature in the attic is within 8 degrees max of the interior (living space) temperature. These homes are energy efficient due to the structure being sealed. However, there is an attic access installed in these homes.

Originally Posted by Ted Menelly

The moisture already gets in...thru the drywall on its normal migration to the exterior. If not vented it will create all and then some of the problems listed above. Of course this depends on the climate as well so to the area in question one would have to know the normal cycle of whether, humidity, freezing, vapor barriers applied or not. In any case...like any attic...there will already be and continue to be heat and moisture. It needs to be vented out.

I did mention structural insulated panels and such above. If there is a loose fill cavity and not solid foam it is better to vent it.

Not if a proper Vapor Barrier is installed. As you pointed out some "Solid Foams" like 2#density will meet this as will Dense Packed Cellulose. And as I stated before, paints and primers that meet the .10 perm rating (Class 1 Vapor Retarder) will not require ventilation.

Originally Posted by champainspectionnews

I agree with you; the basic physics require an air inlet to support an outlet. Otherwise you won't have ventilation and may even draw cool air from inside the home through any openings (e.g., electrical, etc.).

Why couldn't the outlet also act as an inlet. If you open one window in your room with the door closed, you will still get a flow. But if you open the door you will get a better flow.

Originally Posted by Gabe S

Why couldn't the outlet also act as an inlet. If you open one window in your room with the door closed, you will still get a flow. But if you open the door you will get a better flow.

Air will infiltrate an open space like a room through a single opening, yes.

I think the answer you need here is that in order to ventilate a space, air needs to flow through, carrying the bad air out, not just a bit of passive exchange.

Originally Posted by John Kogel

Air will infiltrate an open space like a room through a single opening, yes.

I think the answer you need here is that in order to ventilate a space, air needs to flow through, carrying the bad air out, not just a bit of passive exchange.

True. That is why recommended attic ventilation is 1sf ventilation/300sf of attic space with 1/2 at the low point (soffit) and 1/2 at top (I prefer a ridge vent) , But it doubles if all is at top or bottom.

This dovetails into a related topic. ATTIC FANS:Maybe I will start a new thread on that later....don't want to hi-jack.