DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Insulation and Radiant Barriers > Insulation help in attic/half story





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Old 06-11-2010, 07:13 AM  
swindmill
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I ended up sistering 2x4's to the existing ceiling joists, spacing them 1.5" from the ceiling boards. I then placed 24" wide strips of Reflectix between the joists and above the 2/4s, with the idea being that it would sit 1" - 1.5" from the ceiling boards. Over the Reflectix, I had room for R13 bats, which I stapled in place. The knee walls and end walls are insulated with R19 bats. I realize the Reflectix and R13 isn't enough insulation for a sloped ceiling, so next I'll add polystyrene board to the entire room. All of the unfinished area, including the front gable wall and the sloped ceilling in the side attic is insulated with R13 bats...not much, but it's all the joists/studs would allow, and it is unfinished (I did seal off the only vent I had (gable) because it's such a small area and it's now insulated).

I have IC rated recessed fixtures in, and I noticed yesterday that they are hot to the touch. I do need more insulation in the top attic area before putting up the polystyrene. The Reflectix and the R13 bats meet at the ridge, but there's obviously a gap there. I'm thinking about laying a 16" bat up there (that's about how wide it is) and then stapling a strip of Reflectix below that.

The bottom line is, it's still HOT in the room, but I still have the polystyrene and drywall to go. If anything I've laid out above is clearly wrong, please advise and I'll correct it before continuing. Thanks for the help so far.



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Old 06-11-2010, 11:02 AM  
Perry525
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May I suggest that you buy an infrared temperature gun.This will enable you to measure the outside temperature of your roof from the ground and to scan the inside of the roof to see what you have achieved.
You can scan the parts you have completed and compare them with the part that remains to be insulated.

This will enable you to compare the early morning temperatures inside before the sun gets going. With say mid afternoon when it is really hot.

These temperature guns are really handy, they will indicate the surface temperature of anything you point them at.

Get close for a small area, like the room side of the roof between the rafters where you have placed your insulation and the room side of the roof where it is fixed to the rafter and where you have the maximum conducted heat.

Bats only really work when they are sealed in a plastic bag or an airtight box - the problem with them is that the warm air moves through them and round them, and worse still they cannot be fixed between the joists or rafters to ensure an airtight seal. Add to that they are transparent to water vapour, that easily passes through on its way to landing on the nearest cold surface, leaving the possibility of mould and wet rot.

The reflective membrane is supposed to be positioned an inch below the inside of the roof, to enable the radiation from the sun to be reflected back out through the roof. It should be continued down between the rafters until they meet the top of the walls.

Insulation should then be positioned immediately below the reflective membrane, between the rafters.

The rafters support the sloping part of the roof.
The joists run horizontally supporting the ground floor. They make the ceiling of the ground floor rooms and the floor of the upstairs.

The knee walls have insulation between the studs.

All of the room sides of the rafters, joists and knee walls should be covered with tightly butted polystyrene, preferably two or more inches thick, to stop the heat moving by conduction through the wood framing, the polystyrene on the ceilings and walls and knee walls is then covered with drywall. The floor with floor boards, plywood, or oriental board, as you prefer.

Drywall is important! It provides a half hour fire retarder - this will be important should you ever have a fire.

The recommendation for a heat tight, no energy required home in a very cold, or very hot area, is 14 inches of polystyrene. Temperate areas require less, but every year the recommended level of insulation goes up, therefore it is down to you to decide how much.

Where you are five inches of polystyrene will make a large difference but, one has to accept that, there is a play off between what is desirable from an energy saving, and comfort providing point of view and what is possible because of the nature of the building.



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Old 06-14-2010, 08:59 AM  
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I will look into a temp. gun. If they aren't too expensive, it certainly seems like a nice thing to have. I would have liked to used 5 + inches of polystyrene, but the cost was too high, and because of the odd spaces and obstacles between the rafters, it would have been very difficult to get a tight fit.

I did get the radiant barrier in there as you described, at least as best I could given the flexible nature of what I used. I imagine it collapsed towards the roof in some places. It seems that the area that remains hot to the touch is where the rafters meet at the top of the roof. This is obviously also where the radiant barrier and batts meet, leaving a small gap. The recessed fixtures I've installed there are hot to the touch. I need to figure out the best way of dealing with this.

I will put as much polystyrene as I can on the room side of the rafter and studs, taking into account the need for head space. I really hope that when I finish this, the room won't be the sauna that it still is. I've begun gutting the bathroom upstairs, and I'm now leaning towards ripping out the existing drywall and insulation in the bedroom. I'm thinking about putting in 2x6's in these two rooms (at least the bedroom, as the floor is lower), and having someone use spray foam insulation. I really want the bedroom and bathroom to be very comfortable living spaces.

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Old 06-14-2010, 11:12 AM  
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You can get them from Amazon for under $25.00

Understand, things like this are always a compromise.
Where you have odd shapes to fill, spray foam in a can is a great help.

That's where polystyrene sheets come in, laying or sticking the radiant barrier to the top sheet of polystyrene makes fitting a lot easier.

You can buy a type of plastic can to fit over, this helps to stop the spread of fire.
Then cut a hole in some polystyrene to fit round and over, if you do not insulate the fittings, these will be a weak link, as you write, they do get hot.

Spray foam is the best you can buy, while being expensive, you can buy and use DIY kits thereby saving on paying someone for their time.

Once you have bought the infrared gun, you will see just how hot the different parts of the roof and rafters get. You will see how hot the outside of the roof is and how much of that heat comes in. Then after fitting the polystyrene and radiant barrier between the rafters, you can measure again, to see the amount of heat held back by the polystyrene and the heat coming through the roof and rafters by conduction.
This will enable you to finally decide how thick a layer of polystyrene to fix across the inside of the rafters etc.

In very hot places 14 inches of polystyrene fitted over the roof in a system called SIPS, using a sandwich of polystyrene with Oriental board on both sides, provides a total break between the shingles and the inside of the home, getting rid of conduction of heat through the framing really works wonders, and as the roof is sealed there is no movement of air by convection.
Something to work towards when you can afford it.

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Old 06-14-2010, 11:24 AM  
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Do you think that the radiant barrier and batts, currently in the new room (closet), is doing much at all? I plan on adding the polystyrene and drywall and moving on to the bathroom and bedroom where I may just pay for someone to spray foam when I have the money. I've looked into the DIY kits, but they seem to be several thousand dollars. I'm afraid to discover what someone would charge to come out and do it.

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Old 06-14-2010, 01:25 PM  
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Dow $400.00 delivered for 16 cubic feet - wild? It will go no where!
Add the cost of someone doing it!!!!

I would think not, the problem is, they allow air and heat to move through and round them, they are a bit of a waste of time, insulation needs to be a tight fit, if hot air can circulate round an object, then it does, and the insulation effect is lost.

DIY is best, take your time, do it carefully, use cans of spray in the odd corner.
I am sure you will be pleased with the final job.

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Old 09-28-2010, 05:12 PM  
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We are experiencing a similar issue with our house. I would love to see more pictures of the ways you remedied the situation.

I've read some of this thread and I'll continue later and hopefully contribute. Thanks for the share.

Cheers

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Old 11-10-2010, 04:32 PM  
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My half story has become a much bigger project than I planned when I started this post. For cost reasons, I've put it off for quite a while but I'm getting ready to get going on it. I'm having a large dormer added in the next month and then I'll be having the entire underside of the roof spray-foamed. As I've said elsewhere, I have no soffit vents or ridge vents, so I'm having the spray foam directly applied to the underside of the roof. After all the research I've done and after what I've learned in this thread and elsewhere on this site, I really don't see any other feasible options, and I want the half story to be a comfortable space in 90 degree weather.

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Old 11-12-2010, 03:06 AM  
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I notice that you do not say how thick the foam will be.
Kindly note that foam shrinks over the first 5 to 10 years by 15%.
This can result in gaps at the top where cold patches develop, leading to condensation and damp during the winter and hot patches during the summer.
This also means that the overall thickness declines and more heat comes in.
You must ensure that you watch the person who sprays the roof, to make sure he lays on the thickness you have paid for.
Do make some discrete marks at the thickness you are paying for, making it easy to check progress.
Note, If you do not ensure the correct amount is sprayed on, you will almost certainly end up with less than paid for.
A lot of these people work on the basis of. Out of sight.....you won't know what they did.

You must also take into account that the rafters in the roof need to be insulated.
The rafters are in direct contact with both the world outside and the air inside the room.
Most heat enters a room from the outside by conduction, the route, roof to rafter, rafter to drywall to air.
You must line the room side of the rafters with at least 2 inch thick polystyrene or similar.
With an outside sun temperature on the roof of 86f you will measure 82f on the inside with a one inch thick layer.

We all have our own idea of comfortable.
Mine is to keep our home around the 72 f all year round.
To achieve this in our bedroom ceilings we have 5 inches of polystyrene, 3 inches between the joists and 2 inches below the joists.
In our sun lounge where we have large windows floor to ceiling on three sides East,South and West, to help make up for this we have ceilings with 8 inches of polyurethane foam, 6 inches between the joists and 2 inches below.
In our lounge and dining rooms we have 7 inches of polystyrene, 4 inches between the joists and 3 inches below.

The above may help you to understand insulation and the effect, large windows, location and orientation have.

As an aside, our bedrooms on one of the hottest days of this year 98f =71f inside.

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Old 11-12-2010, 10:59 AM  
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I appreciate your continued input. The existing rafters have a depth of 4", but aren't completely even. I plan on sistering 2x4's 1.5" off the underside of the roof, giving me 5" depth between the rafters. I could then put polystyrene over the rafters with the 5" of foam above. There are too many imperfections in the "ceiling" to do a really good job using only polystyrene boards, which is why I'm going with spray foam. I also 3 gable end walls and the dormer that will be spray foamed.

As soon as the dormer is built, I'll be pulling the existing drywall and insulation out myself. When that's finished, I'll have the spray foam put in, and after that, I'll be putting up new drywall with a friend of mine. So, I'll have ample opportunity to see the finished product when the spray foam is done.

Let me know what you think.



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