Insulating a basement - Page 2 - DIY Chatroom

organick · 10-30-2009, 10:14 AM

Quote:

Originally Posted by ccarlisle

Well, there you go, organick, at least we're narrowing down the problem and the choices you have where you are...so no high humidity but mould issues and heating/insulation issues nonetheless.

Well one thing is for sure, you don't need a vapour barrier like some of us have, but you may need a vapour retarder - that is, if it one is called for. And as I said, insulation may be required...but the type and thickness may be different from what we need. You have tricky situation of controlling where the drying of the basement walls goes to: to the inside if your inside is drier than the outside say in winter - or the reverse...You may have more concerns with water coming in after a rainfall, where the gutters take it and how much if any outside water is coming in from underneath - as opposed to worrying about air infiltration etc.

Wood shouldn't touch concrete; concrete is naturally highly alkaline for a number of years before it becomes just alkaline so no studs directly against the wall, and preferably foam underneath the bottom of the wall.

As far as I know fibreglass is inert and therefore doesn't support life forms such as mould and mildew. Given there's mould everywhere and that fibreglass can become moist, that doesn't mean mould won't grow on it - but it won't eat it they way it eats the paper off drywall panels and wood. Mould neeeds only a few things to thrive: food and humidity being paramount. Provide no food and controlling the humidity with good ventilation are just as good recommendations up here as would apply down there...

mold will def grow in fiberglass insulation. I've remodeled enough bathrooms to asure you of that. Secondly from what I have read you always want to be able to dry to the inside on below grade walls because soil will always be higher moisture content.

I'm thinking xps on the block then unfaced in the wall cavities.

ccarlisle · 10-30-2009, 11:13 AM

Oh, for sure, you see mould in and on fibreglass - but fibreglass isn't of itself a food for moulds. Other moulds or mildews on the other hand are...Yet, this doesn't preclude using fibreglass in shower stalls however because now we "waterproof" showers using the same "vapour barrier" concept - as we now know the problem.

And sometimes you do want moisture infitration and drying below grade. In cold zones and in certain types of exterior construction, you don't - as in my particular case. We limit it...but up here a bigger concern is what is called air transport in the articles.

organick · 10-30-2009, 12:07 PM

Quote:

Originally Posted by ccarlisle

Oh, for sure, you see mould in and on fibreglass - but fibreglass isn't of itself a food for moulds. Other moulds or mildews on the other hand are...Yet, this doesn't preclude using fibreglass in shower stalls however because now we "waterproof" showers using the same "vapour barrier" concept - as we now know the problem.

And sometimes you do want moisture infitration and drying below grade. In cold zones and in certain types of exterior construction, you don't - as in my particular case. We limit it...but up here a bigger concern is what is called air transport in the articles.

yeah all mold needs is air and water to grow anywhere...................

I was just saying in below grade you will never be able to get walls to dry to the outside because the soil moisture content is too high.

joan518 · 10-30-2009, 12:50 PM

Was reading all these posts and we just studded one wall of our basement to put kitchen cabinets on. We used treated 2x4 studs but they touch the block. This wall is next to a crawlspace that the ceiling will be insulated in and all is below grade except about 3' or so that is inside the crawlspace. We didn't put a moisture barrier because it caused condensation and were planning on just using densboard (paperless drywall that uses fiberglass instead of paper) Are we doing this right? You sound very smart and have obviously researched this a lot. Any tips? Should we also use foam?

ccarlisle · 10-30-2009, 01:03 PM

Joan, it depends where you are, and what your house is made of...there's no one correct answer because there are too many variable that affect your particulat structure...

yummy mummy · 10-30-2009, 01:06 PM

ccarlisle, where have you been, I miss you.......

joan518 · 10-30-2009, 01:11 PM

O.K. Thanks Carlisle.

ccarlisle · 10-30-2009, 01:11 PM

Hi YM...missed you too! have been around but not as much on this forum. Hope you're doing OK!

yummy mummy · 10-30-2009, 01:16 PM

Yes, CC I am doing Ok.
Hope all is well, and do remember that we miss you here, with your wealth of info........

Hey, I can kick butt now with ceramic installation. I have it down to a T....

Almost done, all 700 square feet....

organick · 10-30-2009, 03:43 PM

Quote:

Originally Posted by joan518

Was reading all these posts and we just studded one wall of our basement to put kitchen cabinets on. We used treated 2x4 studs but they touch the block. This wall is next to a crawlspace that the ceiling will be insulated in and all is below grade except about 3' or so that is inside the crawlspace. We didn't put a moisture barrier because it caused condensation and were planning on just using densboard (paperless drywall that uses fiberglass instead of paper) Are we doing this right? You sound very smart and have obviously researched this a lot. Any tips? Should we also use foam?

from what i have been reading the DOE recommends that all basements be insulated with a ridgid foam against the walls. Correct me if I am mis-reading that...

The other thing is I would be careful using all pressure treated to frame a wall. When it dries that wall might be as wavy as the ocean.

hyunelan2 · 10-30-2009, 04:01 PM

I am also in the design phases of finishing my basement. I talked to our chief building inspector (I work for a city) and asked him what he would recommend for insulating. This is what he told me (note: we are located in the Chicago area, age of house is 7years old, poured concrete foundation).

He said that the XPS boards are nice, but overkill and not very often used in our area. He recommended just framing 1" off the concrete, and using regular fiberglass batt between the studs. He said that putting the insulation all the way to the floor will make little difference, and that in an 8' basement, you only really need to insulate the top half, since the ground below about 4' of depth is a pretty-constant temperature. However, since insulation isn't very expensive, you can do the whole thing for piece of mind.

He also said that if there is a concern about moisture, put a poly barrier between the concrete wall and framing. (which would keep any moisture away from the wood and insulation). Again, he didn't think this was absolutely necessary and another "piece of mind" step.

Prior to any of this (at this point another building inspector joined in) they both recommended using a sealer, even something as basic as killz, on the walls and floor. The other inspector recommended scraping/chipping anything away from where the concrete walls join the floor and sealing it with a polyeurothane caulk. Caulk any cracks and expansion joints. Also caulk and cover sump pits and other areas where radon gasses can seep into the basement. This will help mitigation efforts, if you need them.

Not that it's the best, most correct, or the way I'm going to go about doing it, but I thought I'd share what I was told.

organick · 10-30-2009, 10:57 PM

Quote:

Originally Posted by hyunelan2

I am also in the design phases of finishing my basement. I talked to our chief building inspector (I work for a city) and asked him what he would recommend for insulating. This is what he told me (note: we are located in the Chicago area, age of house is 7years old, poured concrete foundation).

He said that the XPS boards are nice, but overkill and not very often used in our area. He recommended just framing 1" off the concrete, and using regular fiberglass batt between the studs. He said that putting the insulation all the way to the floor will make little difference, and that in an 8' basement, you only really need to insulate the top half, since the ground below about 4' of depth is a pretty-constant temperature. However, since insulation isn't very expensive, you can do the whole thing for piece of mind.

He also said that if there is a concern about moisture, put a poly barrier between the concrete wall and framing. (which would keep any moisture away from the wood and insulation). Again, he didn't think this was absolutely necessary and another "piece of mind" step.

Prior to any of this (at this point another building inspector joined in) they both recommended using a sealer, even something as basic as killz, on the walls and floor. The other inspector recommended scraping/chipping anything away from where the concrete walls join the floor and sealing it with a polyeurothane caulk. Caulk any cracks and expansion joints. Also caulk and cover sump pits and other areas where radon gasses can seep into the basement. This will help mitigation efforts, if you need them.

Not that it's the best, most correct, or the way I'm going to go about doing it, but I thought I'd share what I was told.

Putting the insulation to the floor makes little difference??? That makes not much sense. The gap would obviously allow for easier airflow and heat lose. The R value of insulation is resistance so no insulation would mean extremely easy airflow.

I am not an expert but from my research it seems that many people highly recommend avoiding batt insulation in a basement because of the potential for it to hold moisture.

RobQuillin · 10-30-2009, 11:35 PM

The issue that comes with fiberglass is that it dosn't mold itself, but it hold moisture and it is and insulator wich promotes mold to grow on the framing and surfaces around it. I own a remodel business here in Michigan and what we see is mold growing in walls where there was a continual high moisture content in the walls behind the framing, especially without an air gap. If the basement was a relatively dry basement there wasn't much of a problem if they left an air gap behind the wall. One thing that you have to remember is that the insulation usually is a secondary insulator rather than a primary insulator. The foundation wall will be the primary insulator. In Michigan it isn't necessarily against code not to have a vapor barrier but some inspectors like them and some don't. It is really a personal preferance here. I would determine the vapor berrier issue by assessing which side of the wall the moisture is coming from. If it is from the inside humidity I would skip the berrier because the moisture will penetrate through the drywall and fiberglass and hit the vapor berrier and get trapped between the berriers and insulation and that is a breeding ground for mold. If the moisture is coming from the foundation wall then a berrier would be smart.

concretemasonry · 10-31-2009, 01:27 AM

You never know how fiberglass was stored, handled and treated on the job site. The dirt and foreign material reduce the insulating value. Even without moisture the fiberglass and some other materials (non moisture repellent materials) lose insulating value. If moisture (as little as 1%) is present it can reduce the insulating value dramatically. This reduction in the insulation reduces the temperature in the insulation and can lead to condensation on the fibers, which will not the removed since it is in a "vapor retardant" environment or there is little air circulation or movement to cause the moisture to be removed even though it is not absorbed, but is held physically. This coupled with any adjacent materials or the contamination of the the fiberglass and support mold that will hold more moisture and grow, depending on the temperature and any increasing moisture supplies.

Because of the flooding of several feet of water during Katrina, many ceilings had insulation that held enough moisture from the humidity to cause the weight of the "drywall" and fiberglass celing systems to collapse after the water receeded. Some people did not even bother to renail the studs to the plates with new corrosion resistant fasteners, so the walls will be questionable in a few years. Some even drywalled over the old damp insulation to add insult to injury.

Dick