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Squished 09-18-2012 10:56 AM

Attic insulation in MA - Strange problem
 
Hi all,

New to the forum, and hopefully can use it as a resource to learn more about DIY projects and share my experiences while DIY'ing my entire house renovation.

Preface: I live in Massachusetts, and I currently have a $50,000 building permit on a $350,000 home that was build in the 1920's that I purchased in July 2012. I'm in the process of renovating the 1st and 2nd floor, basement and attic are staying as-is.

Problem: During my inspections, specifically my rough framing, the inspector told me I need to not just insulate my renovation areas to code, but also the other areas of the house, including the attic to R-38. My attic currently has an existing 3/4 tongue and groove floor over 2x6 joists with a large AC unit and duct work laying on it. On the floor below, 80% of the ceilings are removed which allowed me to install R-21 in 80% of that attic floor/2nd floor ceiling. That leaves 20% of the ceiling uninsulated due to existing ceilings on the 2nd floor and the finished floor on the attic. The roof is comprised of exposed 2x8 rafters, a layer of 3/4 tongue and groove sheathing, a 3/4 layer of foam insulation (r-7 maybe?), the roof paper and then the shingles. My dilemma is that my only option to get the R-38 is spray foam, which I simply cannot afford right now (I'd literally not make my mortgage payment that's how tight the budget is as I anticipated using batts). I had hoped by getting r-21 in the 80% exposed and R-30C in all the rafters, he would let me slide until down the road when I renovate the last 2 rooms on the second floor, but that's a no go.

The more and more I read the code, I'm seeing that if it's "existing space" then I'm not obligated to bring it to code, meaning my r-21 and r-30c efforts would be beneficial, but not subject to inspection. The first and second floor renovation areas are subject to inspection, which is understood. Also, if I read the code correctly, that my 3/4 foam insulation on the roof needs to account for a minimum of 40% of my R-value in the rafters, how is that possible when I need to get to R-38 yet the roof is already existing and redone only 5 years ago?

Any insight or recommendations would be great. I want to live in this house sooner rather than later so I need to pass my insulation inspection completely to get my CO.

Thanks in advance.

Other important factors:

-No ridge vent
-No soffet vent
-2 small 12x12 windows on each gable end.

Windows on Wash 09-18-2012 05:40 PM

Are you going to be conditioning the attic (i.e. converting it to living space)?

If not, why is there foam on the underside of the roof deck?

Leave the attic as unconditioned (i.e. vented and outdoor space). Pull of the floor board and air seal all the top plates and penetrations. Once that is done, blow in R-50 cellulose. Much cheaper and easier than batts.

Seal all the ductwork connections while you are up there.

Squished 09-18-2012 07:09 PM

Quote:

Originally Posted by Windows on Wash (Post 1012652)
Are you going to be conditioning the attic (i.e. converting it to living space)?

If not, why is there foam on the underside of the roof deck?

Leave the attic as unconditioned (i.e. vented and outdoor space). Pull of the floor board and air seal all the top plates and penetrations. Once that is done, blow in R-50 cellulose. Much cheaper and easier than batts.

Seal all the ductwork connections while you are up there.

Never will condition it to living space. As for the foam, no clue, the roof was put on 5 years ago by the previous owner who has been deceased for 2 years. No paper trail of why/how.

The floor boards can't be pulled. There's a brand new $10,000 AC system sitting on half the floor. It's all plumbed in and wired and I'm not moving it.

I've got to come up with another option.

Windows on Wash 09-19-2012 07:17 AM

You can cut up around it. That is not an issue as you can pull the floor in sections.

Squished 09-19-2012 07:30 AM

I really don't want to pull up a 1920's finished T&G floor....it's in REALLY good shape and finishes the attic floor really nicely for storage.

Windows on Wash 09-19-2012 07:48 AM

You are going to need to decide what you want the attic to be.

If you want it for storage, prepare to have moisture issues or spend much higher dollars on different insulation techniques or materials.

If you want to treat it as conditioned space, spray the roof deck and count on expanding your budget considerably.

If you want the home to just be vented correctly and efficient, pull up the boards, air seal, loose blow insulation.

This is certainly one of those situations that you can't always have your cake and eat it too...without it being a very expensive cake. :eek:

Squished 09-19-2012 07:54 AM

Quote:

Originally Posted by Windows on Wash (Post 1012869)
You are going to need to decide what you want the attic to be.

If you want it for storage, prepare to have moisture issues or spend much higher dollars on different insulation techniques or materials.

If you want to treat it as conditioned space, spray the roof deck and count on expanding your budget considerably.

If you want the home to just be vented correctly and efficient, pull up the boards, air seal, loose blow insulation.

This is certainly one of those situations that you can't always have your cake and eat it too...without it being a very expensive cake. :eek:

Oh, I'm going to have the cake and I'm going to eat it too. Every crumb. My cake is from Walmart. Taking the floor up is 100% out of the question, it's never happening.

I think my final decision is that I'm going to put faced R-30c in the rafters, no vents in the rafters, put 21 over the T&G floor to account for the 20% I'm missing and pass my inspection. I'll replace the 12x12 windows on each end with gable vents.

Windows on Wash 09-19-2012 08:29 AM

The Walmart cake isn't bad stuff.

Just so you know, insulating the rafters/roof assembly and venting the attic (i.e. gable vents) are at odds with each other.

Your air barrier (envelope) and insulation layer should occupy the same plane in the home.

In this case, if you are going to insulate the roof, it should be continuous and therefore no ventilation will be required. The issue with that insulation schedule in the roof is that the rafters will still be ice cold as a result of the less than R-8 value in them. That being the case, any moisture in an unventilated attic assembly will condense on the rafters and create a mold, mildew, rot issue.

Theoretically you can add the combined R-Values in different planes if the attic was not vented. This is not the case here.

I am sure that Gary has some technical data he can provide so I will wait for him to weigh in.

Squished 09-19-2012 08:39 AM

Quote:

Originally Posted by Windows on Wash (Post 1012892)
The Walmart cake isn't bad stuff.

Just so you know, insulating the rafters/roof assembly and venting the attic (i.e. gable vents) are at odds with each other.

Your air barrier (envelope) and insulation layer should occupy the same plane in the home.

In this case, if you are going to insulate the roof, it should be continuous and therefore no ventilation will be required. The issue with that insulation schedule in the roof is that the rafters will still be ice cold as a result of the less than R-8 value in them. That being the case, any moisture in an unventilated attic assembly will condense on the rafters and create a mold, mildew, rot issue.

Theoretically you can add the combined R-Values in different planes if the attic was not vented. This is not the case here.

I am sure that Gary has some technical data he can provide so I will wait for him to weigh in.


Ok, I think I'm following you here. Basically I'm OK to do the floor and rafters, just don't do vents, period. I have no soffet vent, no ridge vent, and I'll scrap my plan to replace the two 12x12 windows on opposite sides with gable vents and just leave them closed.

I think the foam board that is on the roof is maybe an R-3, if that. It's 3/4 and on top of the sheathing. If I had my choice, I wouldn't put R-30c in the rafters at all, just leave them exposed. However, I'm being forced to put R-38 in my attic due to renovation on the floors below. There's no where else to get 38 but to do 21 on the floor and 30 in the 2x8 rafter.

My attic is a nice walk up attic with nice wide stairs from the 2nd floor. if it was a pull down attic system, I'd say forget it and just rip the floor and blow it all in thick as can go. Since it's usable storage space that we need, I'm not going to lose it.

Clutchcargo 09-19-2012 08:54 AM

I had the same similar issue.
I'm in Massachusetts too; Boston area. I was told R-30 for the attic which is about 9-10" of pink. I hemmed and hawed but ended up tearing up the T&G attic floor and adding a 2x4 sleeper edgewise to get the space I need to get the R-30 in there and put a floor back. I am only putting down about 6 sheets of plywood for storage. The rest of the attic will be un-floored.

Edit: I agree with you about the existing space.

Squished 09-19-2012 09:15 AM

Quote:

Originally Posted by Clutchcargo (Post 1012906)
I had the same similar issue.
I'm in Massachusetts too; Boston area. I was told R-30 for the attic which is about 9-10" of pink. I hemmed and hawed but ended up tearing up the T&G attic floor and adding a 2x4 sleeper edgewise to get the space I need to get the R-30 in there and put a floor back. I am only putting down about 6 sheets of plywood for storage. The rest of the attic will be un-floored.

Edit: I agree with you about the existing space.

Thanks for the reply. Unfortunately my floor is only 2x6 in the attic, so I'd need to do at least a 2x6 riser to give me enough to get my R-38 rating in the floor. The T&G simply can't come up, 40% of it is covered in brand new duct work and AC unit. It would do me no good and I'd kill myself doing it.

Gary in WA 09-20-2012 12:06 AM

Posts #6,8, pretty much summed it up... It sounds like you need to ask the Inspector how he would suggest you insulate it to code. Having two separate thermal barrier planes will do nothing, you cannot add them together for a sum, as WoW said correctly. With the HVAC up there, and your need to have attic storage, you do have a unusual situation. He may suggest to; build some walls/ceiling around the HVAC unit, insulate the rafters (only above small room) with fiberglass/foam board and airspace above, insulate the rest (outside the room) with blown-in cellulose/f.g. to keep the heat/cold in the rooms below and the ducting above, housewrap the back of the knee-wall to prevent wind-washing.
This is the only way I see to "go around" getting the required insulation under that unit and still keep the attic "vented" for moisture removal. The heat escaping from the unit may keep the Inspector happy and the room conditioned. You may need room-air supply if gas fueled.

Foam; above or below the roof deck- for unvented attic; http://www.buildingscience.com/docum...rchterm=attic+

Thickness of foam required in chart, bottom of pp. 71 -map of U.S.; http://www.buildingscience.com/docum...n-roof-venting

I'd be interested in the Inspectors answer, let us know please...

Air seal the attic first; http://www.google.com/url?sa=t&sourc...wWATQw&cad=rja

Gary

Squished 09-20-2012 04:25 AM

Gary,

Sounds like I have alot to think about. The inspector told me you can add the floor plus the rafters to get the required value. From what you're saying, you can't. When I have the inspector at my house for a first and second floor insulation inspection tomorrow, I'll run my plan by him for the attic and see if he'll pass it. If he passes it, that's what I go with. for my own knowledge, what is wind washing? Regarding the thermal barrier, isn't that already establsihed on the roof line since I have a 3/4" foam board across the entire roof?

Thanks.

Squished 09-20-2012 04:54 AM

EDIT: The more I think about the thermal plane, my existing conditions, the fact I have no ridge or soffit vent, I think I have a way I can do this. I'm going to insulate the rafters inside the "room" of the attic with r30c and drape it down the back of the knee wall to meet the ceiling. I'm going to put two layers of 21 across the ceiling behind the knee walls. Here's a crude picture of what I think my thermal plane will be (blue is HVAC unit, brown is T&G floor):

http://i222.photobucket.com/albums/d...ps3163f8b0.jpg

This is going to leave part of the rafters exposed, which will be good for ventilation and prevent snow from melting at the edge of the roof and creating ice dams due to no vents. The two layers of 21 will make R-42, the 30c in the ceiling plus the foam board hopefully makes 38, if not, I'll just cover the inside rafters with a thin layer of foam board to make the 38 needed. This creates me a nice thermal plane, creates a method of ventilation, and will prevent the snow from melting at the edges of the roof. Maybe I'll cut in a ridge vent later. A win-win? Thoughts?

FYI: The reason for using 21 behind the knee walls, I have a TON of unfaced 21 leftover.

Squished 09-20-2012 07:00 PM

Any input on this layout?


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