Does my roof need ridge vents?

[JTK]

Sorry if it's been suggested, but the quality of the ridge venting is as important as the venting itself. Like said, depending on the configuration of the house and the wind it sees, you can have problems with ridge vents or any vent that penetrates the roofing.

I have some inlaws that live in a huge, newer built home. One with all kinds of peeks and valleys to the roof. They have one area in an unfinished upstairs room where water comes in from the ridge venting when the wind and rain is just right. I suspect they have it going on elsewhere, but it hasn't presented yet through the drywall that I've seen.

If you don't have nice wide open soffet venting, any roof vent is pointless.

 

[BMWTurboDzl]

Originally Posted by KrisZ
Originally Posted by BMWTurboDzl
Originally Posted by henni

4. Re-directed a 10% HVAC air-flow (in/out) into the now encapsulated attic space.



This is extremely important for keeping the roof sheathing of an UNVENTED attic dry. Unfortunately building code hasn't caught on to that in many locales.

Why would you waste energy to ventilate an unoccupied space when the laws of physics and thermodynamics can accomplish the same thing for free? Provided everything is set up right initially. Home heating and cooling is expensive as is and will only increase in cost, to propose directing conditioned air into an attic is lunacy.



When creating an un-vented attic you bring this attic space into the housing envelope. Technically when creating an un-vented attic there is no insulation laying on top of the drywall ceiling below. The most common type of spray foam to use is open cell. Open cell spray foam isn't a vapor barrier so moisture (showers, cooking, breathing, etc) can migrate into the attic foam and collect at highest point in the roof to cause roof rot.

Having a small supply/return vent in this space prohibits moisture accumulation.

The problem is that building codes out of fire* concerns don't normally allow a supply/return in an un-vented attic but there are ways to mitigate that concern.


*Lack of drywall makes it easier for the framing in the attic to catch fire and embers could get distributed to other areas of the house because they get sucked into the return duct.

 

[KrisZ]

I guess warm states can be different. My house in CA doesn't have a vapor barrier, but in Canada, the living space is always encapsulated by a vapor barrier and then insulated. Attic space is the same. The ceiling has a vapor barrier, and there is a thick layer of blown in insulation on top of that. The rest of the attic is simply vented by sofits and ridge vents. If done correctly, there will be no moisture accumulation inside the attic at all and no need to include the attic into the living envelope and waste energy conditioning air inside it.

 

[BMWTurboDzl]

Originally Posted by KrisZ
I guess warm states can be different. My house in CA doesn't have a vapor barrier, but in Canada, the living space is always encapsulated by a vapor barrier and then insulated. Attic space is the same. The ceiling has a vapor barrier, and there is a thick layer of blown in insulation on top of that. The rest of the attic is simply vented by sofits and ridge vents. If done correctly, there will be no moisture accumulation inside the attic at all and no need to include the attic into the living envelope and waste energy conditioning air inside it.



I'm only talking about un-vented roofs. What you're talking about is for vented roofs and specifically cold climate (vapor barrier). The vast majority of attics built in the US use vented roofs like what your described but without the vapor barrier.

 

[KrisZ]

Sorry for not being clear. I understand you're talking about unventilated attic, but the original response to henni was in relation to him making the attic unventilated.
I questioned that move. Why make an attic unventilated and waste energy heating and cooling that unused space? Especially since he mentioned energy saving. But from his post, I gather the saving were actually from better equipment installed and better insulation. Additional energy savings could've been achieved by making the attic vent like I mentioned earlier.

I can see doing what henni did would improve comfort on the second floor, since the temperature difference between it and the attic would be a bit less, but from energy savings point of view, it is not the best solution.

 

[BMWTurboDzl]

Originally Posted by KrisZ
Sorry for not being clear. I understand you're talking about unventilated attic, but the original response to henni was in relation to him making the attic unventilated.
I questioned that move. Why make an attic unventilated and waste energy heating and cooling that unused space? Especially since he mentioned energy saving. But from his post, I gather the saving were actually from better equipment installed and better insulation. Additional energy savings could've been achieved by making the attic vent like I mentioned earlier.

I can see doing what henni did would improve comfort on the second floor, since the temperature difference between it and the attic would be a bit less, but from energy savings point of view, it is not the best solution.


In the United States almost every home built on a slab has the HVAC system and/or duct system in the attic. It's a fairly large energy penalty because the system and/or the associated duct work have to overcome the additional heat/cold (Ducts themselves are only insulated to R6/R8). In addition duct systems leak and if they're in a vented attic it is not only a loss of energy($) because now you're heating/cooling the outside, it also slightly depressurizes the house so it pulls outside air in through air leaks.

Creating an un-vented attic brings the attic HVAC system inside the housing envelope.

 

[KrisZ]

I totally forgot to take the HVAC system being in the attic into account. Thanks for clearing that up. Yeah it makes more sense it this case to make the attic part of the conditioned space.

In Canada the furnace and the blower are in the basement, well out of extreme temperature differences that an attic has.

 

[henni]

https://www.creativeconservation.com/unvented-attics-a-better-attic-system

Quote
A fundamental requirement of an unvented attic assembly is the use of air-impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic. This reduces latent air-conditioning loads and provides further reductions in energy consumption.

In hot climates, unvented attics are ideal where HVAC equipment and ductwork are located in the attic. Modifying the attic to create an indirectly conditioned attic space with Icynene can significantly reduce energy consumption.

 

[StevieC]

You can never have enough venting. Heck in your climate I would install a thermostatically controlled attic fan to move a breeze through there. One time installation will extend the life of your roof largely there after.

 

[spk2000]

When I lived in Lexington KY I had a very energy efficient home that had a powered vent that was controlled by temperature and humidity. It has 2 Natural gas furnaces and 2 AC units - each in basement or attic. Also had the knee deep blown in insulation and great champion windows. Before that house I thought Champion windows were low end.

 

[JTK]

I know several of my family members had their 120v fan driven "mushroom vents" replaced when they had their shingle roofs replaced. Within a few years the fan motors burned out in them. You need to check on those from time to time. These were supposedly high quality units.

 

[StevieC]

Originally Posted by JTK
I know several of my family members had their 120v fan driven "mushroom vents" replaced when they had their shingle roofs replaced. Within a few years the fan motors burned out in them. You need to check on those from time to time. These were supposedly high quality units.

They have brushless solar operated units now, which is nice because they only spin when the sun is really beating down and slow down on overcast days.

 

[doitmyself]

As often happens here, people are offering advice based on their region. I'm glad that a few of you brought up the concept of unvented attics. Unvented attics and HVAC in the attic are not common in the northland.

Some advice here is off base just a bit. I.E., the amount of soffit vent vs. roof vent needs to be be somewhat balanced. Most sources suggest removing gable vents if you install ridge vents in order to make the system operate best. Problems can come up with powered attic vents also. You can create negative pressure and suck conditioned air out of your living space.

I suggest that gregk24 research what's best for him in Florida and his particular house.

 

[4WD]

Originally Posted by doitmyself
As often happens here, people are offering advice based on their region. I'm glad that a few of you brought up the concept of unvented attics. Unvented attics and HVAC in the attic are not common in the northland.

I suggest that gregk24 research what's best for him in Florida and his particular house.

Some advice here is off base just a bit. I.E., the amount of soffit vent vs. roof vent needs to be be somewhat balanced. Most sources suggest removing gable vents if you install ridge vents in order to make the system operate best. Problems can come up with powered attic vents also. You can create negative pressure and suck conditioned air out of your living space.


To work in conjunction with a radiant barrier (in the south) see my reply …