Beamed ceiling insulation advice

[70SATMan]

I've got a typical 1961 Cal ranch house on the Central Coast. 2x8 T&G Fir open beamed roof. 4x6 beams on 6 ft centers. So, of course no roof insulation. The original roof was tar and gravel which sucked balls and we replaced it with 30 year asphalt shingles. The exterior roof insulation was very expensive at the time so, we opted out of that.

We want to insulate and drop the ceiling down to cover the rafter beams so that I have enough clearance for installing recessed lighting throughout. We've never had soffits or ridge vents and based on the condition of the roof when we re-roofed, decided we didn't need them. That was with the open ceilings.

SO, looking for advice on the insulating material. While most of the info out there recommends air gaps, there is thought that in a situation like mine, no gap is better. As long as the vapor barrier is to the living space. Would you recommend rigid foam or fiberglass batting? The fiberglass would be easier to install lighting but, I may be able to get better R out of the foam and then deal with the cans into it. Also, I'll be attaching the electrical wiring to the underneath of the roof T&G.

Last but not least...Over the new interior insulation will be 1x6 T&G wood. No rock. So, do you think the 6 ft centers of the rafter beams is to long of a span? My gut tells me it'll sag. Should I just bite it and add additional nailing strips? The new nailing strips would need to be 2x6 on edge to block the open areas out. Can't imagine that 3 ft centers would sag..

[island911]

fiberglass batting -easy to stop the air movement.

"1x6 T&G wood." ...cedar? Oak?

Well, really, doesn't matter, you can keep the insulation up with string (zigzag between the beams) then the T&G is easy. ...1" 6'OC should be fine.

[TimT]

Pictures would help.

[Bob Kontak]

Originally Posted by island911

1" 6'OC should be fine.

Seems a big honkin' gap to be hanging upside down across. You sure this is ok?

[island911]

Well, take a board of the stuff, set on two sawhorses spaced 6' apart and decide if the deflection is too much.

1" T&G is pretty thick for having to carry only its own weight.


...moisture gradients will likely cause bigger deflections.

[island911]

I'll add that having the extra 2x6 nailing strips will act as thermal bridges as well as extra expense of materials and installation. OTOH my balance of soln maybe unacceptable. (it's your money - your call)

[syncroid]

Sorry, probably out of the norm, but my husband Syncroid asked me to take a look at your dilemma. I work with contractors and builders on a daily basis (I'm a realtor, don't bust me too hard) and have worked with a lot of renovation homes, especially Eichler's in the South Bay. Ok, enough about the creds......

Since you have an already established composite material on the exterior of the roof, I have seen the best insulation between beams with a foam based material. I have a great local company that can talk you through the pros and cons.

With regard to the the T&G wood interior material on 6 foot span- it will sag. You need to install additional support.

Hope this helps.

Wife of Syncroid
Leslie Heinrichs & Ian Humphries - Home

[19-911-65]

Michael:

Sounds like a nice project you are considering. I would highly recommend consulting a structural Engineer and let that person evaluate what you have and help lead you to where you want to go. My first impression is that the existing roof structure is iffy at best without adding the additional weight. If nothing else chat with your local building codes office and/or a local reputable residential building contractor.

Insulation you may want to consider, as mentioned before, is fiberglass batt insulation w/a vapor barrier. Manufactures like Owens Corning and Certainteed will show on their websites typical installation procedures and I would be surprised if they did not recommend an air space between the glass batt and the underside of the existing roof substrate. This can be achieved with Styrofoam spacers from soffit to ridge. In general terms R30 or more (10-12”) would be a minimum starting point. Also there is closed and open cell field applied blown foam or ridged foam sheets. I would also recommend opening up the exterior soffit and add ridge vents (at least with fiberglass batts). This is primarily to evacuate the heat (and moisture) that will build up between the underside of the exiting roof and the insulation. It will also elongate the life of your shingles. Blown fiberglass insulation may also be an option to you.

Ceiling application of 1x6 T&G sounds nice…best on 16”centers if not 24” centers. Six foot centers are far too wide apart to apply this type of material on. There are many different ways to add blocking or dead wood to facilitate 16/24” centers. This can even be achieved by attaching a 2x2 to the underside of the existing ceiling, plywood gussets and another 2x2 nailer for the 1x6 to attach to. The issue will be if the existing structure is there to carry the additional weight/load.

Most recessed canned light rough-ins require the insulation to be pulled back from around them…sometimes as much as 12” so as not to create a fire hazard. Surface mounted track lighting, while not what you stated, can be less of an overall issue.

There are a lot of ways to skin this cat…get someone to confirm your ideas so your job will be done right the first time around.

Best of luck,

Glenn

[70SATMan]

Originally Posted by TimT

Pictures would help.

Well, not a picture of my ceiling in particular but, the construction is the same as this though that looks like 3 ft centers on the beams. Mine are 6 ft OC. that and my ridge beam is twice as tall and laminated. That'll get recapped.

[70SATMan]

Originally Posted by island911

fiberglass batting -easy to stop the air movement.

"1x6 T&G wood." ...cedar? Oak?

Well, really, doesn't matter, you can keep the insulation up with string (zigzag between the beams) then the T&G is easy. ...1" 6'OC should be fine.

Been looking at either cedar or knotty pine for the finish. I like the look of alder as well.

[masraum]

Since you don't have any sort of venting for the existing roof, I would think that sprayed in foam would keep you from having to worry about that. The reason that I say this is that if you have a house with soffit and vents up top (ridge or barrels) and you want to go to foam, you have to seal the space (get rid of the vents) (and condition it, I think, when there's an attic). Since you won't have any space, and don't currently have any vents, that sounds perfect to me.

Originally Posted by 19-911-65

Most recessed canned light rough-ins require the insulation to be pulled back from around them…sometimes as much as 12” so as not to create a fire hazard.

Yes. I do think it's possible to purchase cans that are rated for having insulation right on them. I assume they are more expensive, but in this instance, it may be worth the extra expense.



But in the case of both of my comments, I'm far from expert. I'm just a dude with a house.

[70SATMan]

Originally Posted by syncroid

Sorry, probably out of the norm, but my husband Syncroid asked me to take a look at your dilemma. I work with contractors and builders on a daily basis (I'm a realtor, don't bust me too hard) and have worked with a lot of renovation homes, especially Eichler's in the South Bay. Ok, enough about the creds......

Since you have an already established composite material on the exterior of the roof, I have seen the best insulation between beams with a foam based material. I have a great local company that can talk you through the pros and cons.

With regard to the the T&G wood interior material on 6 foot span- it will sag. You need to install additional support.

Hope this helps.

Wife of Syncroid
Leslie Heinrichs & Ian Humphries - Home

Just might drop you a line Leslie thanks. I've worked with the Dow Thermax professionally and for a four inch cross section beats fiberglass but, it's pricey (around $60 for 4 inches of 4x8 and its foil backed.

I guess my biggest worry is whether I really need the air gap or not with the 2" roof substrate. Even uninsulated, we've never had issues. I've heard of screwing and glueing the rigid and calling it a day.

I wonder if I put in an air gap without airflow if that might not be worse.

[rsNINESOOPER]

I just completed a project for a client that included a similar dilemma as the one you describe.

#1 DO NOT use foam insulation with out using sheet rock unless you like dangerous
house fires with deadly smoke and quickly spreading flames.

At a minimum it would be necessary to add a joist between each existing joist so the span between is not too far for installing the T&G or sheetrock. I would be willing to bet the cost to re-roof with foam insulation and install the T&G will be similar. Just get estimates for both and you will have your answer.

As far as lighting solutions go there are several options that a sophisticated contractor could install by installing the necessary wiring. The wiring can be hidden by adding architectural details to the existing open beam design that will look like they belong. I have done this sort of thing a few times on homes such as yours and an Eichler in the Bay Area. Another poster above referenced this iconic mid century developer who favored this open beam method of home design in entire bay area developments.

So many people before you have approached this very problem of insulation and lighting being added at a later date. Personally I prefer the roof insulation and integrated lighting solutions as opposed to sheetrock and cans which take away from the look of these homes. In my opinion it would be kind of a shame to cover up the open beam ceiling detail but that is just my opinion.

There are lots and lots of builders, contractors, and carpenters out there but few are able to think outside the standard box and fail at executing refined details and or solutions to integrating wiring and lighting into an existing open beam detail.
Choose wisely and good luck with the project.

[billybek]

Originally Posted by rsNINESOOPER

I just completed a project for a client that included a similar dilemma as the one you describe.

#1 DO NOT use foam insulation with out using sheet rock unless you like dangerous
house fires with deadly smoke and quickly spreading flames.

Choose wisely and good luck with the project.

I was going to mention adding a layer of 5/8 drywall over the foam on the ceiling, but RS9 beat me to it. This is a big deal to add a fire resistant layer over foam.

His post offers some good advice.

[URY914]

Looks like my Grandmother's house.

[island911]

"#1 DO NOT use foam insulation with out using sheet rock unless you like dangerous
house fires with deadly smoke and quickly spreading flames."

hmmm... would really matter? I mean, by the time fire burned thru an inch of cedar, the place would be filled with plenty of deadly smoke and quickly spreading flames. I wouldn't use foam for other reasons, but smoke toxicity is not one of them. ...because I can't think of a good house-fire smoke.

Span sag: Every span sags. Even steel floored buildings have camber built in such they become closer to flat when they sag with people and their stuff.

On SAT's house... I expect that if anyone asked the Q of "New construction roof, 2x8 flat, on 6' centers of 4x6 beams -okay?" people would say NO - too flexy/saggy" --Is it?

What is the span of those 4x6 main beams? ...will adding the weight of 5/8 sheet-rock (+ extra hangers/nailing-strips) be too much? -- a falling structure can kill faster than fire. ...since we are being extra safe here)

Maybe you should ditch the idea of F-Glass insulation with cedar covering and go to Aerogel insulation with Nomex honeycomb panels. ...don't forget to instal redundant fire suppression systems.

Vapor and venting: Just what is the climate there? Most venting that I see strikes me as complete over-kill. But then again my POV comes from handling the water vapor that drives to the outer skin of a jet - you know, bags of moisture breathers in an aluminum tube flying in -100+ degree air. (big moisture gradient, as it freezes to the inside of a non-permeable surface)

Anyway, that's my 2¢ worth, but you know I'm unconventional, so you may just want to knock it all down and build something to today's code. --else it's all wrong.

[kach22i]

I would find lights that don't required to be hidden in a ceiling cavity, pendant mounted cans or something pretty.

Rip the old roofing off and install some roof SIP's (Structurally Insulated Panels), cover with a white rubber membrane roofing, or metal roofing, or light colored shingles if the pitch is warranted by the manufacturer.

LED light fixtures, smart light switches which know when you are in the room will save you a lot of money in the long run.

ALTERNATE: If you really wanted to seal the roof up tight, consider spray on foam insulation and finishing as discussed. There is some soy based stuff out there which you should research before deciding.

I went to a lecture recently which provided lots of information. This is the main speaker's website.

http://web.me.com/kellygrocoff/missionzerohouse/Home.html


Here is a local (to me) supplier of the smart switches.
http://www.ferguson.com/

[dipso]

Originally Posted by masraum

Yes. I do think it's possible to purchase cans that are rated for having insulation right on them. I assume they are more expensive, but in this instance, it may be worth the extra expense.

The cans are IC and Non IC. IC you can bury, Non IC you can't.
IC stands for Insulation Contact. About the same price.

[70SATMan]

Lots of good info you guys..and just so you realize, going to be doing all the work myself. I do my own gas/water plumbing, electrical, framing, dry wall (though I hate it). I've done complete roofing with my father but, I had mine contracted because I have a flat roof carport and didn't want to mess with installing the membrane so, I left the roof to the pros.

However, I'm 10 yrs in on a 30 year roof so, I'm not going to re-roof unless we go up with an addition. At the time the additional weight of the foam/OBX sheathing needed for the exterior insulation route gave me concern with the 6 ft OC beams. My roofing contractor felt the same. The cost delta at the time was substantial as well.

Island....interior 10 ft beam span. Also, the ridge beam is supported in the center of this section of the house (behind me in the pictures) by a full 3/4 masonry fireplace wall 3 ft thick that runs from the crawl space (with it's own footings) all the way up to the roof line. On the back wall is an open walkway from the dining area into the living room. Our climate here on the Central Coast is nearly Mediterranean.

At any rate, my place is an L shaped layout wrapped around my carport with only the backside of the house utilizing the open beam roofing. Of that open beam section we only really see one half of that in my dining room/office and a little more than half in my living room. Interior walls and drop ceilings cover the rest so, it's not like I'm covering a ton of detail and it'll still be cathedral when I'm done. At this point we have new track lighting on the ridge beam in the living room...That'll stay. We haven't settled on the dining area lighting yet but, I only need two cans in the office which is off the dining area.

Couple of pics:

Living room






Dining area looking at the new office:




It'll be easy to add the additional nailers for the new T&G. Tying that into the ridge beam and the exterior wall top sill plate will alleviate weight concerns for the new interior ceiling. I was just trying to avoid more work, heh heh. Pretty much knew the answer to the question when I asked it...Just need you guys keeping me honest. Going to go with 24"OC.

If I go foam, I will only use the Dow Thermax. It's foil backed both sides and rated for exposed use so, no need for rock over that as an additional barrier. I'm more than comfortable going right over it with the new finish T&G ceiling. Even though it's more expensive, I get R26 for four inches over R15 with fiberglass batting and that's without dropping the ceiling any lower than the beams (plus the 1" T&G).

I have enough room right now with the Thermax to get a 1 inch air gap.

My biggest question still is whether I really need the air gap with either insulation type since I don't have soffit or ridge vent air flow. If its safer to have it than not, then I just have to space the foam down with furring strips. If I stick with FG batting, then I'm going to need to drop the entire ceiling down to get an air gap and then I can get R19 up there.

Keep the comments/suggestions coming...good or bad...Its all good...

[Zeke]

I've done this. You're right in that if the air flow has no exit, it's not going to help as much as mass. I did this with rigid foam. Wires went up first, then the lights and finally the foam.

We had more beams; less spacing, so center nailers were not necessary. What I liked was that we held the finished ceiling up a bit so that the original beams still showed. That breaks up the ceiling for a nice look, especially painted somewhat differently.

That's what I'd do with yours. I'd box the existing so they were deeper and fill in between with 3" foam and your T & G. You will need nailers at the beams and one down the center.