# Whether Or Not To Vent Roof



## Crazyjake8493 (Sep 26, 2014)

Hey everyone, first post on the forum here. I've learned a lot from reading, but I've come across something I can't quite decide on.

I've got a 1930's Cape Code Style house, 1.5 stories with short upper attic and side attic space behind the second story kneewalls. At some point, two rooms were added on to the back side of the house, along one of the eaves, not the gable walls. The addition spans the width of the house, and the lower slope roof of the addition meets the original roof just above where the original eaves were. 

My main attic has gable vents on both ends, no ridge vents, but the soffits are not vented anywhere. I've been working on insulating the attic floors and kneewalls and I know all the problems associated with insulating 1.5 story houses. I'm also planning on adding soffit vents on the front side of house (opposite the addition) and rafter baffles to make sure air gets up to the upper attic and out the gable vents. In the rooms in the addition, I've taken down the acoustic ceiling tiles and furring strips, and plan to put up drywall, but I've been planning to insulate the 2x6 joists with fiberglass batts. The soffits on this addition are not vented, and have pieces of fiberglass batts stuffed in behind the fascia to block and air leaks. Where the roof meets the side attic there are pieces of sound isolation board tacked in place.

Sorry for rambling, but on to my question.. Since I have access to the side attics of the main roof, where the soffits were before the addition, should I vent the soffit of the roof on this addition, with baffles in the rafter bays, and connect this roof to the side attic and main roof, so that air would come in through soffits of the addition, and then up through the main attic out the gable vents? Or leave this soffit unvented and only vent the soffits on the side of the house opposite the addition?

Thanks in advance
Jake


----------



## joecaption (Nov 30, 2011)

Missing some important info.
#1, Really should have included your location in you profile, not just mention it in your next post.
#2, Not one picture so we can see what your talking about.
#3, Fiberglass insulation does not block air flow. 
No vented soffits, the gable or any other roof venting is all but useless. Try sucking on a straw with your finger over the end out it, same principle.


----------



## Windows on Wash (Aug 30, 2011)

Jake,

Post up a picture like Joe said. It will elicit more responses.


----------



## Perry525 (Jan 10, 2010)

These days we have a better understanding of air flows and heat. If you think of the best designs - Passive House, roof ventilation is a no no.
The passing wind causes a low pressure area above and down wind of a home, this pulls the air from the home, which is then replaced by outside air....cold in winter, hot in summer.


----------



## Windows on Wash (Aug 30, 2011)

No offense Perry, but you won't find a home that is less Passivhaus than a Cape Cod.

Depending on the style and type of a home, venting a roof assembly is far safer than considering it part of the conditioned space. 

There is a long way to go from most of the construction and Passivhaus.


----------



## Perry525 (Jan 10, 2010)

*Super insulation*



Windows on Wash said:


> No offense Perry, but you won't find a home that is less Passivhaus than a Cape Cod.
> 
> Depending on the style and type of a home, venting a roof assembly is far safer than considering it part of the conditioned space.
> 
> There is a long way to go from most of the construction and Passivhaus.


You are so right, trying to move things into this century, and getting people to understand that the historic way is not always the best.


----------



## ThatDaveGuy (Dec 31, 2010)

I feel that the important point here is that the concept of Passivhaus can be applied in many ways to reno/refit upgrades. You won't get anywhere near the level of new construction specifically designed with that in mind, but you might be able to integrate a lot of the features over time to cut energy usage substantially and improve overall comfort levels.


----------



## Crazyjake8493 (Sep 26, 2014)

Sorry, didn't have any way to upload any decent pictures at the time, or I would have. I've decided to open the soffits and install rafter baffles, allowing me to connect the airflow up to the original soffits and vent the entire attic again.


----------



## HDS (Jun 21, 2014)

Crazyjake8493 said:


> In the rooms in the addition, I've taken down the acoustic ceiling tiles and furring strips, and plan to put up drywall, but I've been planning to insulate the 2x6 joists with fiberglass batts. The soffits on this addition are not vented, and have pieces of fiberglass batts stuffed in behind the fascia to block and air leaks. Where the roof meets the side attic there are pieces of sound isolation board tacked in place.
> 
> Thanks in advance
> Jake


How do you plan on insulating the area where there is no venting? One issue I ran into in a similar situation was my stairwell ceiling had soffits blocked and at the top no ridge vents or place for the air to go. This is basically an unvented cathedral ceiling. Our roof was replaced and they installed some fiberglass batts as there was no insulation in two of those 3 rafter bays with baffles. 

The issue now though, is it is only an R18ish, and humid inside air can migrate up and condense on the cold roof deck in the winter months. With no air flow, mold and rot may become a problem. We'll probably be dropping the drywall and using closed cell spray foam to get to an R33ish and that'll also be a good vapor/air barrier.

But the humid air movement in the winter time maybe something you want to take into account. 

HD


----------



## begal (Jul 23, 2014)

You need ridge vents. Where will the air go? I have the same house but they call them WWII houses here because they built them after WWII... 
Anyways, the reason you want this is to get rid of humidity from the house. I put in 2 layers of insulation then 2" of foam, then 6mm plastic. Behind are the baffles.
Do you have a metal roof ? I had one too! You might start there and take off the roof and sheathing and aline the baffles. Make sure you have a good VB on the inside.


----------



## Nailbags (Feb 1, 2012)

Crazyjake8493 said:


> Hey everyone, first post on the forum here. I've learned a lot from reading, but I've come across something I can't quite decide on.
> 
> I've got a 1930's Cape Code Style house, 1.5 stories with short upper attic and side attic space behind the second story kneewalls. At some point, two rooms were added on to the back side of the house, along one of the eaves, not the gable walls. The addition spans the width of the house, and the lower slope roof of the addition meets the original roof just above where the original eaves were.
> 
> ...


Most building codes require a ratio of 1/150 -- ventilation space to attic floor space. 
So take your total attic floor space and divide it by 150 and that will tell you 
how much ventilation space is needed and you can see how much more you need or if your ok.


----------



## Windows on Wash (Aug 30, 2011)

begal said:


> You need ridge vents. Where will the air go? I have the same house but they call them WWII houses here because they built them after WWII...
> Anyways, the reason you want this is to get rid of humidity from the house. I put in 2 layers of insulation then 2" of foam, then 6mm plastic. Behind are the baffles.
> Do you have a metal roof ? I had one too! You might start there and take off the roof and sheathing and aline the baffles. Make sure you have a good VB on the inside.


That...looks like the biggest PITB to have done.


----------



## begal (Jul 23, 2014)

Windows on Wash said:


> That...looks like the biggest PITB to have done.


It was a lot of work (and still drywall ) that's why it is good to buy a house cheap with lots of problems because even houses without water damages can have a bad roof with no sofits. So we had to replace the roof due to rot anyways. THe interior the guy had cover up a lot of crap, so that was good to remove it. It's worse if you pay full price for a house then realize this sort of thing like no baffles.

If you don't vent your roof then you'll have a 'hot roof.' But it would be stuffy and possible cause the roof to rot. Then when the roof rots you can replace it install the baffles. For a hot roof you should have r30-40 and with the baffles r40-50. so i've heard...

You can tell when the sofits are working because you can put your hand there and feel the air moving! Needless to say you house will feel 'fresher' and healthier with proper venting.


----------

