Vaulted Ceiling - Insulation Configuration

It seems that you maybe be having an issue with something else, like too much interior volume for heating and cooling, as an r value of 20 is adequate for most regions of this country. There exists a closed cell foam that is 1/4 in thick, 5' wide and comes in rolls. You can get it with a foil surface on one side. Apply this on the purlins /1"/4" material that the shakes are now attached,/ with the foil side up. Use the foil tape that is available to seal the joints. Add another layer of 1"/4" purlins on every other run that was placed for the spacing of the shakes. This results in anchoring points for the steel sheeting at 16" OC, and an aluminized surface facing outward that is sealed. This results in something call reflectivity, which is even more important than r-value in preventing the exchange of heat/cooling from the inside to the outside and vice versa. It also provides an area for the condensate from the underside of the steel sheeting to collect and evaporate.

As far as the interior ceiling area goes, you might consider reducing that by converting the cathedral to a valted variety. This will reduce the costly cubic feet of area that is both heated and cooled that you cannot benefit from unless you have provided for circulation of the air from that area downward to capture the heat and recirculate it, or in the case of attempting to cool that area, vent it to the outside, possibly through a cupola.

TMF

Hello ginasdad,

I have the type roof you described to replace the shakes, which may have replaced for the same reason, length of service and elimination of fire potential.

Insulating the cathedral style roof actually eliminates the need of a reflectivity barrier; which is normally employed when having an unfinished space (attic) above an insulated ceiling.

With cathedral style you are placing insulation in the rafter bays instead. I recommend using a type of stand-off (biscuit) or 1/4" thick X 1/2" square blocks or strips to the outside of the rafters and apply the steel accomplishing a slight gap between the rafter and sheeting. Then application of a 2.0 LB closed cell impermeable spray foam; one inch thickness directly onto the underside of the steel sheeting. The horror stories resulting of this type process in the past were relative to applying a 1.0 LB open cell foam because air and water will permeate this form of spray foam insulation allowing the corrosion troubles of the past.

No air space is required and the stand-offs allow the foam to seal completely including between sheeting and rafter minimizing thermal transfer through the rafters. the 2.0 LB foam cures hard enough you shouldn't be able to leave a thumb nail imprint and you may add a repellant for vector control.

This is the most cost effective method as you fill the remainder of the rafter bay with the batting of choice.

R-20 value batting without sealing foam = actual R-13 or less.

1" 2.0 LB closed cell spray sealing foam insulation carries a R-6.2 value per/inch + R-20 batts = actual R-26 value

If filling the rafter bay with foam a 3/4" gap should be left between wall board and foam insulation.

I like the new foam because of it's sealing potential, leaving no air leaks at electrical connection boxes (receptacles), around piping, etc..

Hope this helps...

Hello Bwire,

TMF is a retired industrial/commercial/residential Building Contractor. Experienced in most forms of building construction.

{you state! insulating the cathedral style roof actually eliminates the need of a reflectivity barrier.}

The poster states that he is going to install steel sheeting as a replacement for his shake/shingle roof.

It does not matter that the structure is wood or steel, all that is required to create condensation on the under side of the sheeting is a 14 degree difference in temperature between the outer and inner air that contacts the sheeting.

Unless the poster does not care about the moisture that is definitely going to condensate on the underside of the sheeting he would be wise to provide a barrier that will shed the water out from the underside of the sheeting to the exterior of his building.

Failure to address this matter will leave him with water dripping down onto his insulation, reducing and often eliminating it's value.

Mold and decay resulting from excess moisture will ultimately attack the wood framing, brown spots will show up on the drywall or plastered ceiling, and worse than all of this is the fact that the mold growing in the ceiling cavity can cause ill health, even resulting in death for some.

The best product on the market today that is the spray on foam that you mentioned is Icenene. I have specified the use of that product several times. It is excellent when used on side and end walls, and can be sprayed directly to the underside of roof sheeting of all kinds. Where ceiling materials are already in place it can be placed on the upper side of these materials also. I have even had it sprayed on the underside of culvert styled buildings. It worked better than any other product on the market.

You might wish to re-think response! If you have a fax # that you wish to provide for me, I can fax you current info regarding reflectivity, I won't state that your opinion is all wet, but it is a little damp.

TMF

GA. Thanks for the tip on Icenene. How many cans will it take to fill up my daughter's boyfriend's car?

This closed cell foam is generally shipped in 55 gal. drums but I think it can be had in small lots in 5 gal containers. It is a two part material and you will need equipment to apply the stuff, however maybe you could find a little side work filling up your daughters girl friends "boy friends cars". The stuff sticks really well and a little liquid makes a lot of foam. They [the boy friends ] will surely be a "foam'in around the lips".

TMF

TMF,

You missed my point of eliminating the possibility of condensation by sealing and directly insulating the under side of the sheeting preventing a temperature differential causing condensation to occur.

Bwire I do understand your point. I am, however: at a complete loss as to just how you plan to prevent direct contact between the sheeting and the supporting members. Unless you are planning to foam the under side of the sheeting before it is installed. We can keep adding a patch on a patch on another patch until the roof fails from the weight of the patches. From experience of installation, designing structures that I have constructed my self and having to estimate the costs of various methods, I firmly believe that my suggestion is a little more affordable than yours, and will yield better results. BUT, I don't have a dime in this project, and I am not being compensated for my good intention, so "here I am and there you are".

TMF

It would be purposeful to adhere insulation to the sheeting as a process of manufacture indeed.

However we use what we've got right. Use the concealed clips to off-set the panel or Tyvek wrap caps though preferably of thicker cap material.

I just came in from feeding my colony of rabbits and returned to this puter and realized from your remark regarding clips, and it dawned on me that we have yet to determine whether the thread poster is using regular r-panel, pro panel or some other preformed 3' wide panels or the standing seam panels that range from 12" to 24" wide. At any rate, I am content that you have reasonable knowledge regarding the subject to do your own installation, but I suspect that the originator of this thread should have the work done by a professional unless he has family and or friends skilled in working with these kinds of materials. It can be quite difficult to find a little leak in a big roof and very costly to repair.

We will meet again and exchange other points of view I'm sure.

TMF

Thanks ubetcha, I asked for more info on that too

Though it sounds as if the thread poster wants a big bang for his/her buck and may gain enough from the breadth of info available on CR4 to accomplish his/her needs.

I first used Icenene to solve problems on a building that had been constructed for the Knights of Columbus in Lake Placid, Florida, around 1996. It is not advertised as a sealant intended to prevent or patch leaks, but it solved a lot of those problems also.

I have had to remove the sheeting and the steel purlins from steel buildings just because moisture collected between the sheeting and purlins and over time rusted the top flanges to such a significant degree that they were structually unsound. This is the purpose for permitting the water to be evacuated naturally from the under side of the sheeting.

TMF

ginasdad,

You commented about using 2" decking, I'm certain you don't need the decking at all. The Styrofoam will not perform as a vapor barrier at all either.

Post #2 & 3 give you considerable information even in as much as TMF and bwire initially disagreed. We could help more with information about the type/size standing seam metal roofing you intend to use.

I will guarantee you the initial expense of the expanding foam sealing insulation will be back in your pocket at the end of the first heating season. Take a look at these DIY foam kits 2 & 3 pound applications - 2" = R-12+ (about R-6.4/per inch) and take bite out of your heating and cooling costs. It is the sealing capability of these type products that enables the significant improvement of blocking air and water vapor permeation into your heated spaces.

Thanks for all the ideas! I was using the 3" styrofoam because I had salvaged it from a builder who was using one of the styrofoam concrete formwork systems to build a house. Mountains of this styrofoam were going to landfill so I stepped in. The panels are 18" x 48" or some portion of that. I just finished insulating the crawlspace under the house and the effects were remarkable.

The decking was because the supplier of the standing seam roofing suggested a plywood sheathing rather than strapping. I have unlimited wood so it is cheaper to have decking milled than buy plywood. The supplier also suggested tar paper on the plywood for the condensation problem. I will provide the specs on the roofing when I find them. The supplier delivers to the site where the roofing is unrolled and cut to lengths. He would loan me with a machine to close the seam or I would hire him to do the application. My experience has been that experienced installers know the tricks that make the job go well but nothing can replace the diligence which comes from being well informed and doing it yourself. I'm sure the horror stories that professionals uncover when coming after the DIY are numerous but this DIY guy prefers to live with his mistakes rather than pay for someone else's.

I am intrigued by the foam idea. How do I get the foam between the metal and the sheathing/decking. If it hardens in a minute it has to fill a cavity rather than being applied to the metal. If I do fill the space between the decking and the metal won't I have a vapour barrier on the outside of my building envelope rather than on the 'lived in' side of the insulation? Hope I'm not belabouring the obvious. thanks

Good morning Ginasdad:

If you had provided this info with the first posting bwire and I might have been able to solve your riddle much sooner. Now I'll try to make you understand in terms that you cannot avoid understanding.

I'll begin at the top. The crimping machine requires two people to operate. One at the ridge of the building with a rope to drag the machine back to the starting point because it works downward. A second person must be at the eve of the roof to retrieve the machine and place it back on the roof so that the upper person can drag it back to the starting point. These machines have parts that wear out and and can cause you a lot of trouble if you do not know how to use them correctly, and keep them in adjustment. If you mess up with the crimper it can get very expensive.

Next, Unless you have a sealant, such as sprayed on foam or something else that the producer of the steal will accept as an equal and can either be rolled or sprayed on the underside of the panels that prevents condensation, you "MUST" provide an air gap between the underside of the panels and the vapor barrier beneath. If you fail to provide this, the condensation will cause electrolysis that will eat the roofing material up from the underside. I have been paid to re-roof buildings that suffered this problem because no air gap existed between the Steel and the tar paper beneath it. If you do this part of the work correctly the Mfg. warrantee will not be violated.

You say that you have a lot of wood available, that is good because you are going to need a lot of it. And you say that you have salvaged foam panels that measure 18" wide and 48" long and are 3' thick. To use this material you will have to remove all of the shingles/shakes from one side of the roof. You will now have to fill in the area between the strip sheathing, apply a vapor barrier, brand does not matter, , Attach 2"X4" wood framers on edge to the strip sheeting that runs across the roof that the singles/shakes are now nailed, and run them across the roof also and space them 18" apart to receive the foam. As the 2'X4" material is 3 1/2" wide this will allow you a 1/2" air gap as is required to preserve the warrantee on the sheeting panels. If you try to place the foam directly and then apply the vapor barrier you will likely tear holes in the vapor barrier rendering it worthless. This is how the job is done correctly. Anything else is incorrect, and you can take that to the bank. If you were working on a flat/horizontal surface the application would be different.

You will have to make arrangements for a ridge cap of some kind, their are several options here, but you must prepare for this when you start, as it is al lot more work if you have not considered this from the very biginning.

Now I am going to give you the very best advice that I possibly can. The roof is the single most important area of construction to get right on your home. Do it wrong and the repairs are costly, your ceiling can be damaged or ruined completely, and funishings too. I see this every year here in Florida, even roofing contractors get caught when an unanticipated thunderstorm shows up. They have insurance to pay for these damages. "DO YOU"!

AND FINALY: Working on roofs is dangerous business even for the skilled personel. If you or the folks that are helping you fall off, it can easily be fatal. Think about the consiquinces of being sued because your friend fell off the roof.

Saveing money on materials like wood and insulation is very OK, and if you want to be a helper and pass materials up to skilled workers, you could save some more there. However: I can tell from your posting that "you do not possess either the knowledge nor the skills to do this work economically, safely, or correctly.

SAVE MONEY AND SAVE YOUR HEALTH/LIFE,"HIRE A PROFESSIONAL TO DO THIS WORK!

Toomuchfun

Your response is very good advice. I have a relative (by marriage) that was helping do repairs on the roof of a church as a volunteer. He fell, and has had a neck brace on for two years now. He was self employed, and now has no income, nor insurance. The church has refused to pay for his surgery, or loss of income. He sued for the medical expenses. Now the church wants to counter sue him for roof damages he caused.

Volunteer = an action of one's free will

Being involved with several non-profits this issue arises occasionally. It is wonderful when an individuals intent is to offer their services pro bono but then I always raise the liability issue because it's socially enfeebling not to observe the probability of error.

I'll remind everyone of the scriptural lesson of the talents and insist we not expect a reduction of cost but that we except the honest bid and pay full price.

I always suggest a contractor to bill us and if it be so in their heart to consider it a gift in kind, then their insurances cover them and they may get a tax deduction too.

toomuchfun:

thanks for the reply, very clear! I understand that you would apply a vapour barrier on top of the strapping. This would leave the existing fiberglass with vapour barrier on both sides. Is this good? The air space between the metal and the styrofoam would only be vented across the roof and would not benefit from convection to carry off the moisture from condensation. Is my reading correct and if so is this enough ventilation? thanks for your thoughts.

How are ya,

I understand that you would apply a vapour barrier on top of the strapping. This would leave the existing fiberglass with vapour barrier on both sides. Is this good?

No. I think TMF would agree you'd end up with with wet insulation.

Steel roofing doesn't require more reinforcement than shake in fact less is quite adequate. You could tear-off the shakes and the existing wooden backing that supported the shakes leaving the rafters then lay a (click on the hyper link) Dupont TYVEK Attic Wrap. Scroll to the bottom under Literature & Videos click the first hyper link. You'll notice how they install (You can do this yourself with a little help) notice how the air gap is created, see how using the Tyvek method handles vapor and condensation issues. This type may be exceptional for your application.

I am in the preparation stages of becoming a Spray Foam/Sealer Contractor and distributor of Conklin Products, among the various Building and roofing, Agricultural, industrial and household products, Conklin is one of the highest volume distributor of spray sealing foam insulating products for the building industry in North America.

After reading your last post I believe you may be better served by a CPI Foam product using one of their consumer spray foam kit's to seal between the Styrofoam you salvaged and the rafters. And if you decide to use the Tyvek attic wrap you may cut the Styrofoam to size and push it into the rafter cavities sealing two layers of it R-30 using the spray foam kit with the concentrated stream nozzle; it's air infiltration sealing capability is wonderful.

thanks bwire,

I have never thought tyvek was cost effective on walls but I think this application could be dynamite!

I think what I will do is remove the shakes and put full 4" 2x4's on edge on top of every other rafter. That will be on 24" centers. The old strapping for the shakes will stay on if it's in good shape. The styrofoam will go on top of the strapping between the 2x4's. I will make an effort to leave air space between the styrofoam blocks to prevent a second vapour barrier. The tyvek will go on top of the 2x4's and the styrofoam with a 1" vent channel between the styrofoam and the strapping for the metal.

Thanks again for all the thought that everyone put into this project. That doesn't mean you can't add more if you don't think it will work!

In response to the original question, no, do not leave a ventilating air gap between batts and styrofoam. The ventilating air should be the same temperature as outside air, which would mean you would have outside air temperature running in between insulating layers. Effectively the styrofoam would be outside your house. Put the styrofom on the rafters, with the roof ventilated OVER the styrofoam.

From what I've seen on foil faced insulation there should be an air gap on at least one side to work correctly. Typically 3/4" or so. Keep that in mind if you pursue the "reflectivity" idea.

Also, ignore the suggestion to reduce the amount of air in the heated/cooled space. Heat loss is a function of surface area, not volume.

I believe that I made that statement when I stated to put the 1/4" closed cell foam that comes in rolls with foil on one side to place the foil side up and seal the joints with foil tape created for this purpose and then place 1"X4" material (preferable pressure treated) or could substitute 20 ga hat channel thus leaving an air gap between the sheeting/standing seam material. This foil faced foam material serves to reflect heat away and the fact that joints are sealed with foil tape makes this material serve as a vapor barrier.

Also regarding your statement to ignor the amount of heated and cooled air space--????? I don't know just how you determine the size/efficiency of your air handling system where you are from, but in every state and on every project that I have either consulted,constructed,or permitted the interior space measured in cubic feet is the first value to include in the efficiency/size of the equipment needed to either heat or cool the structure, and the efficiency is measures in something we refer to as SEER value.

TMF