Insulation & Soffit vents

[radtek]

I've got next to nothing for insulation in my attic. I'm planning on laying out some R-38 batts. I also have zero soffit vents, and only a gable vent at each end of the house. My bills last year during the summer were ridiculous. I bought a case of soffit vents and plan to install them.

I'm worried about condensation though because it is fairly humid in the south with high temps.

Anyone got a definite opinion on this?

 

[hopdog]

I think your gable vents would be sufficient. How is the insulation in your walls? What style home is it?

If you can afford it I would recommend getting polyurethane spray foam insulation. It has a very high R-value, provides a complete seal, and is prevents any moisture migration.

 

[jbford]

we had ridge vents installed recently (along with new shingles) and they are the shiznitz.

also, why not use pour-in fiberglass rather than batts?

 

[david_42]

When you put in the vents, also install baffles, so the batts don't block them. This will give you good airflow and eliminate any condensation problems. I kicked my ceiling insulation to R40 in every house I've owned.

You might also look into blown cellulose. It does a better job of filling spaces and will cover the joists. It's not a bad job with two people. In either case, If you have any ceiling fixtures, lights, fans, etc. you'll need to put barriers around them.

 

[LooyvilleLarry]

I think your gable vents would be sufficient. How is the insulation in your walls? What style home is it?

If you can afford it I would recommend getting polyurethane spray foam insulation. It has a very high R-value, provides a complete seal, and is prevents any moisture migration.

The Soffit vents are CRITICAL to the house. Here is what happens: The air is drawn in the soffit vents and out the gable/roof/ridge vent via conduction. This also carries out the humidity in the attic. If you don't have these, you can put them in without a lot of pain -- ok, maybe a bit of pain - but little cost.

The Ridge vent is the best for venting, as it evenly takes heat across the roof.

Without adequate ventilation AND airflow your attic will have much higher temps, thus higher energy bills and a shorter roof life. Weigh the cost of a roof in and you'll think soffit vents are cheap.

As for the spray - It is great stuff (ha, that is the name of the canned spray ) but not so much for an attic. It needs to breathe to let the moisture out of the house. As for the walls, you gotta really have some high bills to pay for a post-build spray to make a payoff even in 10 years. My 1 car garage, with OPEN walls, was going to cost $2000 to have it sprayed.

Soffit vents, ridge vents, and R38 open faced bats will be a big improvement. FYI, I blew in the fiberglass to R50 and it went really well.

 

[EvilTOJ]

You could install attic fans on the gable vents to force the hot air out. You should have eave vents for cool air to be pulled in while the fans blow the hot air out. I installed one in my last house's attic, it worked well.

 

[radtek]

It's a 35 yo 3/2 with a 2-car attached. Slab construction and 1140' sq. It doesn't have much in the way of bells and whistles except what the previous owners and myself have installed.

I'm willing to bet there isn't a scrap of insulation in the south-facing walls, or any of the walls for that matter. Retrofitting this aspect... well I just don't know about that. The attic I can address easily.

My brother suggested the soffit vents and at least 12" of blown in insulation. I can easily afford this but I'm alone currently and a DYI'er. I installed 350' sq of the bats over the uninsulated garage last year by myself LOL. If I had realized how poor the insulation was in the rest of the attic I would have done something about it. Now my garage has a better rating than the whole house! LOL!

I'm tentatively planning on laying out a single layer of R-38 and then coming back and laying cross-wise another layer of bats.

oh the joys of home-ownership...

 

[LooyvilleLarry]

radtek- look into the Pink blow in. You'll have to find a buddy to lend a hand, and in san antonio, you'll want to pick up a machine the night before so that you can do this EARLY.

We had a fire in the garage ( no beer was injured ) and had to remove and replace all the insulation in about the same size house as yours. I used the pink blow in and we were returning the machine at noon. A couple of hours and I have insulation up to the cross members!

If you do that, be sure to leave area around where those soffits are gonna be! We noticed the difference right away in the winter - about 12% reduction on bills, and the furnace didn't cycle so much.

 

[GreenwoodRover]

The insulation is important and the single layer r-38 will help, 2 IMO is overkill, Insulation is more for keeping heat in the house, vs lowering cooling costs. The insulation will help, but it's more important to keep the air flow moving in the attic take the money for the second layer on insul and add a powered roof vent or a fan for the gables as mentioned above. You can get them with a prewired thermostat. That will keep the attic cooler and therefore the entier house. If your AC ducting runs through the attic wrap that as well.

 

[radtek]

Yes- I've been up there repairing tattered joints in the ducting. PITA. I plan on insulating the duct-work too. Is there a special wrap for this?

I may do the soffit vents this weekend.

 

[LooyvilleLarry]

That would be a big plus on the blow in - your ducts are insulated under the layer.

 

[springer]

Yes- I've been up there repairing tattered joints in the ducting. PITA. I plan on insulating the duct-work too. Is there a special wrap for this?

I may do the soffit vents this weekend.

I replaced mine with flexible insulated 8 inch ducts. Was easier and no more joints in the run to leak.

 

[chris1979]

from what i understand the correct way in the south to avoid condensation is to have soffit vents and a ridge vent. that being said mine has on soffit vent i dont seam to have a problem but i do intend to install some gable vents.

 

[hopdog]

The Soffit vents are CRITICAL to the house. Here is what happens: The air is drawn in the soffit vents and out the gable/roof/ridge vent via conduction. This also carries out the humidity in the attic. If you don't have these, you can put them in without a lot of pain -- ok, maybe a bit of pain - but little cost.

The Ridge vent is the best for venting, as it evenly takes heat across the roof.

Without adequate ventilation AND airflow your attic will have much higher temps, thus higher energy bills and a shorter roof life. Weigh the cost of a roof in and you'll think soffit vents are cheap.

As for the spray - It is great stuff (ha, that is the name of the canned spray ) but not so much for an attic. It needs to breathe to let the moisture out of the house. As for the walls, you gotta really have some high bills to pay for a post-build spray to make a payoff even in 10 years. My 1 car garage, with OPEN walls, was going to cost $2000 to have it sprayed.

Soffit vents, ridge vents, and R38 open faced bats will be a big improvement. FYI, I blew in the fiberglass to R50 and it went really well.

You are right, soffit and ridge vents are the best. I also neglectetd to look at what part of the country he was living. Here in Maine you can get away with gable vents.

As far as the spray foam goes I was referring to putting it on the ceiling, not the roof itself. Any moisture in the attic would be vented out. The warm air needs a cooler surface to condense and since no cool air can migrate through the foam it cannot happen. The problem with fiberglass is there is still a transfer of air through it regardless of how well it is installed.

I am not sure about cooling in the south but here in the north insulation pays for itself rather quickly. Remember, insulation also pays for itself throughout it's life. It never stops working. It may be worth the investment especially if you plan on staying in a house for a long time. It is also a good selling feature especially now that people are getting more educated about such things.

 

[LooyvilleLarry]

Just a followup to this thread, we just got our new electric bill. This is the "budget billing" so that it is the same one every month and is based on the last six months usage and some magical figures.

Old one. $165/mo new one $101/mo. Louisville, KY. That will nearly pay for the blown in fiberglass (DIY) in the first year !

 

[Bobby_M]

Fiberglass fibers are nasty enough when they're formed into neat batts so I abhor the idea of filling the attic with purposely ground up pieces of the stuff. If you've already got some insulation in there and plan on leaving it, I suppose it would be OK but if you're starting fresh, I like the encapsulated stuff. It makes working with it so much more pleasant.

 

[radtek]

Jeez... Thanks guys. Been busy. Put 20 soffit vents in on the South facing side. Made an imediate difference. Got heat-stroke nearly and drew some blood.

We've been having some extreme temps here so the insulation project is on hold even though I got everything.