# Help me insulate a balloon framed carriage house...



## wrooster (Apr 16, 2010)

Along with a 1930's-era home we have a similarly aged detached carriage house, which was mostly rehabbed by the prior owners. The carriage house has a 2 bay garage downstairs, and upstairs is a loft. The end goal for this project is to make the loft dual use -- for her as a home gym (treadmill, yoga mat, light workout weights), and for me as a small home office as well on days when I don't need to commute into the office. The 2nd floor plan is completely open, with no dividing walls. 

The building itself is approximately 30' x 30', with a fairly aggressively sloped roofline. The framing method is balloon, and kneewalls have been inset into the 2nd floor. For a 1930's-era structure, it is surprisingly plumb and level. 

The exterior of the structure is aesthetically nice, with vinyl siding atop a thin foam backing, over the original lap siding. The roof shingling is asphalt, with probably another 5 years or more to go. There are no gable vents, nor is the roof ridge vented.

Aside, here in the northeastern coastal USA area we typically see +95'F max in the summer, and around 10'F minimum in the winter. Humidity is a factor during the summer months.

Off to the side of the 1st floor garage area is a modern 47Kbtu natural gas-fired furnace, installed to code and labeled as inspected for in 2006. The flue is routed through an stainless-lined existing chimney. I am not going to do anything with the furnace other than redirect some of the HVAC ductwork as needed to better feed the loft above. For summer cooling I am contemplating an add-on coil stack and an exterior condenser unit, or perhaps go with a package mini-split A/C system -- still undecided which would be the way to go there. There is pre-existing 60A split-phase to the structure from the house 200A service. 

To finish off the rehab I plan to firestop all of the balloon framing, insulate, drywall, and then put down an engineered wood floor of some type. Project-wise, I am not in a rush -- this is not in any way primary living space so I can proceed at whatever pace gives good results and as budget allows, or until my wife tells me to move faster. 

My question here is regarding insulation... for which you need to know the following:

1) The building has very short soffits, and minimal soffit vent area -- but interestingly this vent area doesn't really go anywhere. The space at the intersection of the rafters and the top plate has been closed off by wood strips (small, fitted pieces of lap siding, it appears). 

2) As you can see from the attached photos, the geometry of the room/ceiling/roof interface is actually threefold. There is an area of roof behind the kneewall; there is another area of roof directly against the loft ceiling; and there is yet another area of roof above the loft ceiling. 

It is the combination of #1 and #2 which is perplexing me. 

What is the best way to insulate this type of construction?

Thanks!
Wrooster


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## joecaption (Nov 30, 2011)

I'd make a few changes before I insulated. There's lots of waisted usable space up there. I would remove some of those knee wall studs in the middle and change them so there would be a header and cripples above the header and frame up a closet out of 2 X 6's. The closit could then be insulated with R-30 with Tyvek on the back side to act as a wind stop. I'd add 2 X 2's to all the 2 X 4 studs so R-19 would fit everywhere except where the baffles are. There your stuck with R-13.
There's going to have to be foam baffles added from the tops of the knee walls to the cross ties for air flow. R-30 could be used in the flat ceiling area.
In the spring I'd strongly suggest adding soffit vents, and a ridge vent.
The shingles will last longer and it will stay cooler in the summer.
When you get that roof redone I'd have them add a cricket to that chimmney so water will not be directed right at the flashing and have that old failing flasing all redone.


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## Windows on Wash (Aug 30, 2011)

joecaption said:


> I'd make a few changes before I insulated. There's lots of waisted usable space up there. I would remove some of those knee wall studs in the middle and change them so there would be a header and cripples above the header and frame up a closet out of 2 X 6's. The closit could then be insulated with R-30 with Tyvek on the back side to act as a wind stop. I'd add 2 X 2's to all the 2 X 4 studs so R-19 would fit everywhere except where the baffles are. There your stuck with R-13.
> There's going to have to be foam baffles added from the tops of the knee walls to the cross ties for air flow. R-30 could be used in the flat ceiling area.
> In the spring I'd strongly suggest adding soffit vents, and a ridge vent.
> The shingles will last longer and it will stay cooler in the summer.
> When you get that roof redone I'd have them add a cricket to that chimmney so water will not be directed right at the flashing and have that old failing flasing all redone.


+1

All good observations.

That is a large kneewall area and a bit of wasted space unless you are going to use it as unconditioned storage.

Can you get a cellulose hose down the outside wall from the kneewall area?


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## joecaption (Nov 30, 2011)

Opps forgot, do all your wiring first, in my area your going to need hard wired smoke detectors down stairs and up stairs, personaly I would go with Arc fault breakers up stairs, GFI circuts down stairs. The reason being at some point someone may want to convert this to a bedroom.
Down stairs I'd use R-19 in the ceiling with paper toward the floors about and your going to have to add 5/8 fire rock to the ceiling to meet code.


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## AGWhitehouse (Jul 1, 2011)

If budget allows, consider a vented insulation panel on the roof. You'll have to replace your roof to do it, but you're already anticipating that. By using a ventilated insulation panel you can get a continuous thermal layer, vapor control layer, and roof ventilation all in one. That way you won't have to worry with outside air circulating within the structure as noted in joecaptions method. You can truly seal the structure tight to aid in efficiency. Then you can still put in the batt. to add to the thermal value. If you can or choose to afford enough foam thickness, you wouldn't even need batt. insulation at the interior allowing for some interesting space finishing options depending on your tastes.

Here's an image of the panels being installed: http://farm6.staticflickr.com/5267/5654956569_01fd1499bb_z.jpg


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## wrooster (Apr 16, 2010)

joecaption said:


> I'd make a few changes before I insulated. There's lots of waisted usable space up there. I would remove some of those knee wall studs in the middle and change them so there would be a header and cripples above the header and frame up a closet out of 2 X 6's.


Already in progress. :thumbsup:



joecaption said:


> I'd add 2 X 2's to all the 2 X 4 studs so R-19 would fit everywhere except where the baffles are. There your stuck with R-13.


As you can see, I built out the rafters likewise, and I'll continue on the kneewall studs. 



joecaption said:


> There's going to have to be foam baffles added from the tops of the knee walls to the cross ties for air flow. R-30 could be used in the flat ceiling area.


This is the part that confounds me -- 1st, what's required for good airflow? And 2nd, where do I get the air from (you'll see why in a second)? How many rafter cavities do you think I will need to put foam baffles in? Again, the structure is about 30 feet across.



joecaption said:


> In the spring I'd strongly suggest adding soffit vents, and a ridge vent.
> The shingles will last longer and it will stay cooler in the summer.


It hasn't snowed yet this year, and temperatures have been quite warm, so I'm making good progress on this project. 

That said, there is *very* little available area between the top plate and the roof underlay; as I noted previously, someone took great care to fill each and every one of those gaps. I'll attach a picture I took some time ago, perhaps in the light tomorrow I can take a better one which demonstrates more clearly these gap blocks. I don't think I can remove these without causing more problems than I will solve. I could try and do a test bore to see if I can install press-in aluminum vents.

This whole dilemma makes me ponder a sealed attic, but then I wonder if in fact I could get it sealed "enough". 



joecaption said:


> When you get that roof redone I'd have them add a cricket to that chimmney so water will not be directed right at the flashing and have that old failing flasing all redone.


Agree on all counts.

Thanks for the all the helpful insight.

Wrooster


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## wrooster (Apr 16, 2010)

Windows on Wash said:


> Can you get a cellulose hose down the outside wall from the kneewall area?


The structure walls are bare studs, both 1st floor and 2nd, so I have access everywhere needed. That said, I have been fire-stopping the gaps created by by the balloon framing. 

Wrooster


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## wrooster (Apr 16, 2010)

joecaption said:


> Opps forgot, do all your wiring first, in my area your going to need hard wired smoke detectors down stairs and up stairs,


Same here, that's my plan, plus a CO detector as well.



joecaption said:


> personaly I would go with Arc fault breakers up stairs, GFI circuts down stairs.


Yes and yes.



joecaption said:


> The reason being at some point someone may want to convert this to a bedroom.


The township committee would probably have a cow if so. 



joecaption said:


> Down stairs I'd use R-19 in the ceiling with paper toward the floors about and your going to have to add 5/8 fire rock to the ceiling to meet code.


Correct, once I have the wiring back in (there was too much aged BX for my liking) I will put 5/8" Type X on the 1st floor ceiling. Or, I should say "I will pay someone to put 5/8" Type X on the 1st floor ceiling" -- I am the world's slowest drywaller, it's just not my thing. You want anything else done, I am on it. But drywall... 

Wrooster


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## joecaption (Nov 30, 2011)

Your going to have to go back and add 2 X's on top of the blocking you added for sheetrock air sealing, a place to attach the rock to the wal, and a place to nail the base board to. 
Ask around and see what one of those style roofs cost and come back and we will explain about the foam baffles and save you thousands of dollars.
That roof had to be done that way because it has a catheral ceiling and there's no good way to do it from inside.


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## Windows on Wash (Aug 30, 2011)

AGWhitehouse said:


> Here's an image of the panels being installed: http://farm6.staticflickr.com/5267/5654956569_01fd1499bb_z.jpg


+1

Vented nail base is great stuff and gives you the best of both worlds.


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## AGWhitehouse (Jul 1, 2011)

Windows on Wash said:


> Vented nail base is great stuff and gives you the best of both worlds.


It's unfortunate how taboo they are. They're right up there with solar energy systems (passive especially). I guess we enjoy whipping out the check book for our Middle Eastern guardians...


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## Windows on Wash (Aug 30, 2011)

AGWhitehouse said:


> It's unfortunate how taboo they are. They're right up there with solar energy systems (passive especially). I guess we enjoy whipping out the check book for our Middle Eastern guardians...


Ah yes.

That is why it is an especially nice treat reading about Sultan "X" that buys and Audi supercar and has the bodywork redone in stainless steel...just cause he can.

Did you get my email? I had a couple of other questions for you when you get a chance.


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## wrooster (Apr 16, 2010)

Attached is a better view of the "air blocking" done at the interface of the rafters and the top plate. 

The vertical piece shown in the pictures is nailed to the outside face of the top plate. There is no easy way to just pull that out to open up the cavity to get airflow from the soffit vents.

Thoughts?


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## AGWhitehouse (Jul 1, 2011)

wrooster said:


> Thoughts?


Vented roof...even if you don't do rigid insulation with it and insulate only with batts at inside, put the venting outside. It will help with air sealing the envelope which will help with the effective R-value.

2x4's laid flat along the rafters and new sheathing over the top. You said you were doing a new roof anyways...


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## wrooster (Apr 16, 2010)

Any soffit venting ideas based on the pictures above? 

Or should I take another approach altogether and just seal up the attic area? I have been reading up on "sealed attics" and it seems like if you ask N experts you will get N+1 opinions.

Thanks and regards,
Wrooster


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## AGWhitehouse (Jul 1, 2011)

wrooster said:


> Any soffit venting ideas based on the pictures above?


Sounds like your hell-bent on the hardway...spade bit or sawzall are two tools that come to mind...good luck


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## wrooster (Apr 16, 2010)

AGWhitehouse said:


> Sounds like your hell-bent on the hardway...spade bit or sawzall are two tools that come to mind...good luck


I don't know why you think I am "hell-bent" on any specific approach. 

Some folks above advised on using foam baffles to vent from the kneewall to the attic. Following that, now I am asking how I get the air though the soffit in the first place, given the construction method which was employed. 

I even asked whether the situation at the soffits should lead to sealing the attic.

Wrooster


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## AGWhitehouse (Jul 1, 2011)

wrooster said:


> I don't know why you think I am "hell-bent" on any specific approach.
> 
> Some folks above advised on using foam baffles to vent from the kneewall to the attic. Following that, now I am asking how I get the air though the soffit in the first place, given the construction method which was employed.
> 
> ...


I have been reading along...and I gave you the logical approach from the start. Here are the three parameters that, I believe, make the decision for you:

1) You're planning on replacing the roof
2) You are insulating your space that has limited roof member thickness which will limit the amount of insulatable space
3) You eaves are currently sealed and would take a fair amount of effort to open up

Taking those three factors into consideration, the most logical option is to use what rafter dimension you have and insulate it. leave the eaves alone as they are already sealed well to air and would be a PIA to open up. Replace the roof and add the venting via 2x wood strips and new roof sheathing. Buy opening up the eaves you now will have to create the air channels up the rafter bays effectively reducing your insulation thickness by at least 1-1/2" at an R-value loss of approx. 5. So instead of an (6") R-19, you'll have (4") R-13. Add to that the potential air leakages from those flimsy foam air channels and you could potentially lose even more effective R-value.

By venting at the exterior, you can insulate RIGHT NOW and get on with finishing you space. Roofs don't HAVE to be vented, though there are many arguments on shingle life extension but, in reality, alot of warranties actually allow for hot roofs. When you do replace your roof in a year or two or three, then provide the venting system...


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## Windows on Wash (Aug 30, 2011)

This is how I would do it as well.

+1


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