Insulation help in attic/half story

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

That should work.

The remaining weak link will be the new windows.
I solved the problem by having quadruple glazing.

That is, two sets of double glazed windows, with a gap of eight inches between the inner and outer panes of glass, with venetian blinds in between.
This enabled the blinds to block the direct sunlight while reflecting the light into the room.

In the normal way double glazing with a venetian blind, results in the blind becoming very hot and transferring the heat into the room, the second set of double glazing keeps the heat inside the window recess.

If I ever get round to building a home from scratch, I will copy the Europeans, in France, Germany and Switzerland.
They recognize that the best asset is shade, they nearly all have external roller shutter blinds, these are kept in a box either above or below the window and are wound into place eith by hand or using an electric motor, it is a system that keeps the heat outside, leaving the double glazed windows cooler in the shade.
They can of course be stopped in any position to allow light into the room.

Have you thought about spray in foam? Have you had a cold drink in a foam cup in the summer and noticed, no sweat? same thing in your walls. I have been getting the spray foam installed instead of fiberglass for a few years now. It will pay for itself, in heating and cooling bills. The last job I did, I was charged $1.55 per sq ft for walls.

Spray foam is what I'll be using. I got an estimate last Friday. The cost to do the entire underside of my roof at 5", as well as 2 gable walls and the 10x8 wall that I'll have when I complete the dormer, is $1500. He's going to use open cell on that. I was surprised at how inexpensive it was. The same company is going to lay plastic in my crawlspace and spray foam the inside of the foundation with closed cell foam for $600. I'll have some before and after pictures of the spray foam job, so maybe I'll post them here.
Here's where the roof is going to be cut out and raised, and you can see the pathetic insulation job that the previous renovators did; that's R13.


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A lot of people seem to believe that laying plastic sheet over the ground in the crawl space will stop the moisture in the ground from rising and condensing on their joists and thereby prevent mold and wood rot.

This seems to be based on the observation that when you lay plastic sheet on the ground and then lift the plastic sheet there is always condensation on the underneath of the plastic.

The facts are that the temperature in the crawl space is always so low that the air is to all intents dry and the ground is even cooler, the moisture in the ground does not suddenly decide to warm up and project itself upwards onto your woodwork.

Water vapor always moves from warm to cold, therefore it stays where it is. Unless you have large gaps under your home, where freezing air can be sucked under the home by the passing wind. Then moisture will migrate into the freezing air.

The wood of your floor will always be warmer as a certain amount of the heat in your room escapes downwards by conduction and radiation.

This brings me to the spray foam on the inside of the foundation. What is this supposed to do?

As I have written many times, heat always moves to cold.

When insulating your home, you need to keep the heat inside your comfort zone during the winter and to keep the heat out in the summer.

To make this process as economical as possible, the insulation needs to be as close to the comfort zone as possible.

Therefore, placing insulation on the perimeter of the crawl space will do nothing for you in summer or winter.

Placing the insulation on the room side of the downstairs floor will keep the maximum amount of heat both in during the winter and out during the summer.

However, because of the problems caused by raising the floor level, raising door frames etc. most people settle for having the insulation tightly packed between the joists under the floor. As with your roof, the joists then become the weak link and it is usual to fix two or three inches of polystyrene sheet across the floor to keep the heat inside the joists.

There is no point in allowing even a small amount of your expensive heat to escape through the floor into the proportionally vast crawl space, where it will in all probability not even raise the air temperature by one degree.

May I suggest that you use that infrared temperature gauge to read the floor temperature inside the rooms, then read the under floor temperatures and the bottoms of the joists, then the ground and foundations. Get a real idea of what is involved.

I understand your points, and ideally, I would insulate the room side of the floor, while laying a new subfloor over the original heart pine, and then a new wood floor. I have plenty of ceiling height and removing baseboard and door jambs doesn't bother me. The problem is the cost of a new floor. Incidentally, because my heart pine floor is not level, and jacking it up in the necessary places isn't feasible, I do plan on eventually leveling it on the top side and doing exactly what we're discussing. That may be some time from now, however.

Right now, my crawlspace is actually a little bit drafty. I'm hoping to have someone do repair work on the brick foundation, followed by a concrete stucco. Doing that and sprayfoaming the inside perimeter would at least keep the crawlspace as water and air tight as it practically can be kept. My HVAC ducts all run in the crawlspace, and my water heater is down there too. The sprayfoam should at least help in that regard.

You mentioned that the heat upstairs keeps the joists warm enough to prevent them from being moist. My understanding is that for this reason, it is not necessarily a good idea to insulate between the joists. The insulation between the joists will then stop the heat from reaching the bottom of the joists. The only way to prevent this problem is to sprayfoam to the bottom of the joists, completely covering the wood. That would be cost prohibitive, as well as physically impossible in my circumstances. There is so little clearance in my crawlspace that I was surprised when the insulation company said they had people who could get in there.

Thanks for your continued input. I've learned a lot in this thread.

Think of using a steel poker in the fire, leave it in the fire long enough and the heat travels along the bar by conduction and the end burns your hand, to avoid this, perhaps you wrap the end in a rag, insulating your hand from the heat and you can hold it a bit longer. before you get burnt.

The steel bar heats at one end, the heat travels along the bar, and as it does heat is radiated and convected to the sides, with the bar gradually dissipating its heat until it reaches the point where all the heat is lost into the air, and the far end remains cold in your hand. (for a time)
The heat input, being balanced by the heat loss over distance.

Your joists work exactly the same.

The heat is input from the air above the floor.

The heat travels by conduction down the body of the joist, loosing its energy by radiation and convection to the sides as it goes adding a small amount of heat to your crawl space.

Filling the spaces between the joists with insulation, helps slow down the loss by convection enabling the heat to travel further by conduction, leaving the end/bottom of the joist hotter, sooner and longer.

Wood used to be considered a good insulator, then modern insulators like, polyurethane, polystyrene, aerogel etc came along, things that slow the loss of heat to a far greater extent.
And wood became a heat conductor and the weak link in keeping your home warm.

There is little heat loss through the floor, compared with your windows, ceilings and walls.

However, because our feet are in direct contact with the floor, our body heat quickly disappears downwards into the floor and out into the cold sky and we can end up with cold feet.

Something, we do not feel so intimately, with our body's insulated rather more by warm air when indoors, but stand with your back against an uninsulated cold wall and you soon notice the heat loss.

Its interesting, that many people loose a 2 or 3 foot wide strip along their outside walls during the winter, with the heat loss through the air into the walls making that part of the room unusable.

“Kindly note that foam shrinks over the first 5 to 10 years by 15%.” ---- Perry, I’ve researched that statement and only found SPF will shrink only when improperly mixed (two parts).

You may find this interesting: BSI-009: New Light In Crawlspaces — Building Science Information

Why open cell foam/
• “In climate zones 5 through 8, the “air impermeable insulation” must be a vapor retarder (Class II; 1.0 perm dry cup or less), or have a vapor retarder coating or covering in direct contact with the underside of the insulation. For instance, an air impermeable but vapor permeable spray foam (0.5 pounds/cubic foot) would not meet this requirement, unless a vapor retarder coating were applied (R806.4.4).” IRC FAQ: Conditioned Attics — Building Science Information
“On the other hand, open-cell spray foam (average density, 1/2 pound per cubic foot) is not a vapor retarder. Installed at a thickness of 3 inches, open-cell spray foam has a permeance of about 16 perms, making it fairly permeable to water vapor.” A Close Look at Common Energy Claims - EcoHome Magazine A Close Look at Common Energy Claims - EcoHome Magazine
Air seal the knee walls from the sloped ceiling to prevent air movement behind the drywall. Use the ADA: Info-401: Air Barriers
Air seal the attic and install foam board or house wrap on the attic side of knee wall, under and over it: How to Seal Attic Air Leaks | The Family Handyman
http://www.simplesavings.coop/simplesavings/SIMPLESAVINGS knee walls.pdf
Gary

I've only entered "SPF shrinkage" on the internet search, where- outside the U.S.?
Do you remember any more about the article statement? Who, where, why...... ?

Thanks, Gary

GBR said:

I've only entered "SPF shrinkage" on the Internet search, where- outside the U.S.?
Do you remember any more about the article statement? Who, where, why...... ?

Thanks, Gary

Click to expand...

Hi, I was researching the European Common Market, following up on their building research pertaining to Passive House building.

I drop in on this from time to time to see progress.

They have been studying building insulation since the early 1980's. After Denmark managed to produce some very tight houses that were well insulated but subject to shocking levels of condensation and mold.

This was then taken up and followed through in Germany and is now going to be standard all over the EU from 2016.

They are working on the basis, that every possible type and style of home can be built to Passive House standard, which in the EU is about a hundred times more demanding than our standards.

I cannot find the article but, here is a USA document that more or less repeats the information, all be it that its writing about polyurethane.

Polyurethane Insulation Materials

Polyurethane is a closed-cell foam insulation material that contains a low-conductivity gas (usually hydrochlorofluorocarbons or HCFC) in its cells. The high thermal resistance of the gas gives polyurethane insulation materials an R-value typically around R-7 to R-8 per inch.
Over time, the R-value of polyurethane insulation can drop as some of the low-conductivity gas escapes and air replaces it. This phenomenon is known as thermal drift. Experimental data indicates that most thermal drift occurs within the first two years after the insulation material is manufactured. The R-value then slowly decreases. For example, if the insulation has an initial R-value of R-9 per inch, it will probably eventually drop to R-7 per inch. The R-value then remains unchanged unless the foam is damaged.
Polyurethane insulation is available as a liquid sprayed foam and rigid foam board. It can also be made into laminated insulation panels with a variety of facings.

Contacts | Web Site Policies | U.S. Department of Energy | USA.gov

They do of course produce sheets of the stuff covered on both surfaces with aluminium foil, this slows the drift as the leakage is only via the edges.

Sorry I cannot provide any more information, when I can, I will come back on this.
Perry.