# Insulating attic in old house (~1900)



## shatchett (Oct 31, 2019)

Hi all, Sam here. Wasn't sure which forum to put this in, but since it is MOSTLY about insulation I figured I'd put it here. I bought a house in New Jersey this summer. it was built around 1900. I've spent the past months getting to know the house and making a list of things that need doing. First on my list is replacing some of the old knob-and-tube wiring, most of which is doable via the attic. While in the attic I started thinking about what I'd have to do to finish off the space, maybe make some storage or an art studio or an office. There is zero insulation anywhere in the house. But still, the house stayed surprisingly cool this summer on some very hot days with just the A/C unit which is located in the attic.

Ultimately I think I could finish off a small section of the attic, maybe a space in the center that is 10'x12' just to have some more room in the house. The walls at the edge would be 3-4' high but easily enough for a cabinet or drawing table.

Some details:

Balloon construction with hip roof, dormer window on one end
Interior peak is 8'6"
Interior dimensions are about 30'x30' with access all the way out to the soffit
Roof joists are 2x6
Attic floor joists are 2x6 (they'd have to be sistered if I were to make it a room)
Attic flooring is TNG 1x6
Dont see any type of venting to the outside, although the bathroom fan is vented into the attic (tsk tsk)
Most of the roof decking is TNG boards with a few repairs here and there
AC unit is maybe 20 years old, will have to be replaced soon, ducts go only to the 2nd floor rooms
Wiring in attic is a total mix of good and bad techniques with a range of wire types
House still uses radiators in each room

A few photos are below. From a safety perspective, I feel I need to replace the old wiring before I do anything. To do that, however, I'll need to pull up all/most of the floor boards. This has made me pause and question if I should also be adding insulation.

I've read a bit about insulating old homes, and there's even a few very similar posts here on the board. My concern is that old homes were built to breathe and moisture never got locked in. Adding insulation can change that by creating more moisture. In quite a few cases, a simple question like this resulted in "rip the walls open and spray on closed-cell insulation", which I'm not in a position to do. What I want to do is strike a balance between cost and sensibility. Do I need to fully insulate and eliminate all drafts and address the moisture 100%? Can I take a step forward by adding SOME insulation but not FULLY insulating the attic? 

Questions:
1) I'm assuming I HAVE to have ventilation. If I add soffit venting (which I can access), do I need a power fan near the peak? Just adding the soffit would be a big improvement, but for summer heat build-up it may be good to have the fan. I'm not familiar with passive vents, so maybe one of those near the peak? 

2) Would it be possible to insulate the walls and ceiling of the room I wanted to add but not the rest of the attic? I think the stairs could also be insulated from the rest of the attic. This would leave the rest of the attic in its current state. I do not think there is enough space for R-38 (not sure what the options are). I keep thinking that the walls and 2nd floor maintain their temps pretty well with zero insulation, so how would the new room fare with less than R38? Thermally, the new room would be connected to the 2nd floor with no insulation in-between. I'd probably add a baseboard heater for heating and tap into the A/C duct for cooling.

3) I have to rip up most of the floor to correct all the wiring. While I have the floor open, should I be considering the addition of batts (maybe R21?) outside the footprint of the room I'm planning on adding? There would be a much bigger temp difference between the attic and the 2nd floor, which could cause more moisture. But since there is still no insulation in the walls and the house is drafty, is that a problem?

Option 2 is "keep the house closer to original design" and Option 3 is "insulate the whole thing to save some money".There are just so many options and so many things to consider it's a bit overwhelming. I dismissed spray foam on the underside of the roof due to cost, but maybe I can make that back in savings? 

Thanks for reading the whole way through this. I appreciate any feedback, even if it is that I'm thinking about this all wrong.


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## Nealtw (Jun 22, 2017)

You have a whole lot going on there and a lot of good questions. 

Can we first assume the basement is or crawl space is dry and the floors are level and the there is no rot in the house that you are aware of. What condition is the roof in. 

With old houses we always start at the bottom work our way up on framing issues and then look at the roof and work our way back down.


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## shatchett (Oct 31, 2019)

Hi there! Starting from the bottom and working our way up...

The main house is about 30'x30' and has a full basement under it. The foundation LOOKS solid, although there was one section that had a few hairline cracks at the joints (pic added). On the inside of the basement, there's a coating on the wall so that the block isn't visible. I'm assuming it's a parge coating. It looks to have been in place for quite a long time. There's no visible moisture other than the spot where a downspout isn't placed correctly on the outside, so it's dumping water right at the foundation. To me, and to the cranky (but very good) home inspector, the foundation seems to be in good shape. The floor of the basement is concrete and has no major cracks in it. There's a lot of variation in the surface of the concrete, like it was poured at different times. But it's solid, other than the area by the boiler and hot water heater. I suspect it's very thin there (or redone multiple times) due to having had the coal and oil furnaces there in the past. There's a new addition in the back of the house (1 large room and a bathroom) that has a crawl space under it. No major concerns in there, either. I can say, however, that there is no insulation in there, either. I had expected to see some in between the floor joists but there's nothing there. One side of the basement has drywall on it (which I immediately assumed to be in place to hide damage), but it's been in place a long time and it looks like it was put in place to house electrical outlets. That side of the basement appears to have been an office at some point. There's also a front porch (full width of house, covered with aluminum roof) which just has the externally accessible crawl space but I've never been under there. It's open on all 3 sides and covered with lattice. 

First floor is in good condition. Hardwood floors (maybe original?) throughout except for kitchen, which is 3/4" higher and has linoleum on it. The floor is level and good except for a small section between two rooms that seems to have a bump in the floor, as if the floor sagged on either side of the support beam under it. The sag is maybe 1/8" or 3/16". Whole floor squeaks, which is nice because then I know when my teenage kids are sneaking around. 

Second floor is in good condition, but the Northwest corner of the house appears to have settled maybe 1/2" or 3/4". The floors dip towards that corner. This affects part of the master bedroom only. It would have affected the bathroom, but it was remodeled at some point and looks like the floor was leveled. All the doors fit in their frames and close, although they stick sometimes in higher humidity. There are no cracks in the plaster on any of the floors. 

Roof is going to need replacing at some point. There are no holes, and shingles aren't showing staining yet. But in 4-5 years it will probably need it. There's one spot in the attic where there's a small hole in the roof decking and I can see the under side of the felt paper, but the hole is only 1-2 sq in and no signs of water. The chimney leaked at some point. Not sure if it is still leaking, but we've had A LOT of rain lately and it seems okay. But when the roof is redone, I'll have all the decking around it replaced and upgraded. 

The house has vinyl siding which looks like it was applied over the previous wooden siding. All the windows were replaced at some point (vinyl) except for 2 odd-sized windows, which are still single pane wooden windows. These were clad with aluminum but will have to be replaced in the next few years. 

I don't see any signs of rot (other than the frame around the dormer window in the attic). I've been poking around a lot with a screwdriver to check the condition of the wood, and can't find any real trouble spots. I've also scoped a few of the walls to check for moisture, insulation, and wiring, and haven't seen much of any of them. No real signs of moisture damage, either, aside from around the chimney from previous leak. About half of the wiring was redone somewhere along the way, and the service was upgraded to 200A by someone who knew what they were doing (wiring is very neat and orderly). Kitchen and upstairs bath were fully upgraded sometime recently, too. 

Oh, and not sure if this is normal or not, but there are no gutters on the main house. There's a gutter around the font porch, and around the room that was added in the back. But nowhere else.


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## shatchett (Oct 31, 2019)

Forgot to add the foundation pic.


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## Nealtw (Jun 22, 2017)

Well done, you have been looking at things and know a lot about your house. 

I forgot to ask where you are are? 

Hip roof with a room inside has a special set of problems for insulation.
The room you are thinking about, would it include this window.


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## shatchett (Oct 31, 2019)

Yep, that window would be a part of the room. I'm in New Jersey, basically in Trenton (just outside of it). There are A LOT of old homes in the area like this one. I've been looking at them as I drive by them to see how they have been maintained. Everything from siding to gutters to roof material to what kind of doors and windows they have. Helps give me some ideas for my house.


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## Nealtw (Jun 22, 2017)

shatchett said:


> Yep, that window would be a part of the room. I'm in New Jersey, basically in Trenton (just outside of it). There are A LOT of old homes in the area like this one. I've been looking at them as I drive by them to see how they have been maintained. Everything from siding to gutters to roof material to what kind of doors and windows they have. Helps give me some ideas for my house.


 The reason I asked about that area is it has 2 problems, one in the framing and the window is to low for a room. 

It has a great big plus.
The structure is there to make it bigger. If you re structure the roof, that can be done in a way that would make the insulation and venting work and you get a good size window.


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## shatchett (Oct 31, 2019)

Hmm, interesting. That would raise the window and add a ridge for venting. I'm getting quotes for various things just to see what they cost. Not doing all of them, since I'm on a constrained budget. I'll get a quote for this work, just have to find a contractor who could do it.

I'm guessing this wouldn't change the strategy for insulation. But it would change the venting.


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## Nealtw (Jun 22, 2017)

shatchett said:


> Hmm, interesting. That would raise the window and add a ridge for venting. I'm getting quotes for various things just to see what they cost. Not doing all of them, since I'm on a constrained budget. I'll get a quote for this work, just have to find a contractor who could do it.
> 
> I'm guessing this wouldn't change the strategy for insulation. But it would change the venting.


 Venting a hip roof that is not built for venting is near impossible so the rest of the attic, I would do it more like a semi conditioned storage area. 

It is almost like building an insulated shed inside, that allows air to move from soffet vents to the vents at the peak. That would keep the HVAC inside the envelope, and you could leave most of the floor in place. 

Which way do the floor joists go under the window, hoping they point at the window?


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## shatchett (Oct 31, 2019)

Nealtw said:


> Which way do the floor joists go under the window, hoping they point at the window?


Floor boards point to the window, floor joists point side-to-side with the window. So the joists are parallel to the window.


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## 3onthetree (Dec 7, 2018)

If your hip for a 30x30 house comes to a point, then a cupola style vent works so you don't have a box vent on every face (size of vent would have to be looked at though). 

This dormer if necessary could be vented with its own ridge vent, as it wouldn't be connected to the main attic above the new space. The front face with the clipped gable wouldn't be though, and the 1x12? ridge board will make a funky ceiling if you are laying drywall right to the underside of rafters. 

Also, any room you put up there is just a storage room without proper light + ventilation, and no sleeping conversion without window egress.


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## Nealtw (Jun 22, 2017)

shatchett said:


> Floor boards point to the window, floor joists point side-to-side with the window. So the joists are parallel to the window.


That would complicate it a bit, Can you tell where the bearing walls are the joists land on?


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## shatchett (Oct 31, 2019)

I'll draw a diagram and post it here.


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## Nealtw (Jun 22, 2017)

shatchett said:


> I'll draw a diagram and post it here.


If you were doing attic storage, this is what I would do. Finished with drywall.


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## shatchett (Oct 31, 2019)

The drawing you provided is almost exactly what I had in mind. I hadn't thought through it far enough yet to add the poly. I was also thinking of the same/similar for a studio that would get MAYBE a few hours of use a couple days a week. Like a drafting/drawing table and some cabinets and some storage (aside from the window issue that you pointed out). That would, of course, require the A/C and heat modifications, too, neither of which I've thought through yet, either. 

Still working on the load bearing wall drawing.


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## Nealtw (Jun 22, 2017)

shatchett said:


> The drawing you provided is almost exactly what I had in mind. I hadn't thought through it far enough yet to add the poly. I was also thinking of the same/similar for a studio that would get MAYBE a few hours of use a couple days a week. Like a drafting/drawing table and some cabinets and some storage (aside from the window issue that you pointed out). That would, of course, require the A/C and heat modifications, too, neither of which I've thought through yet, either.
> 
> Still working on the load bearing wall drawing.


 With new construction that poly is seldom called for but with odd sized joist and floor boards and lath and plaster it is impossible to get the air seal you want, you might do it wit caulk and canned foam spray. 



The Hvac is best in the room but were best you can drop the ducts between the joists and if it is in the envelope it can be hard pipe or for storage area you could push them out to the perimeter just inside the wall.


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## Calson (Jan 23, 2019)

The old house is already much changed with the addition of the AC mechanicals in the attic. What can be effective is adding an inch of spray foam insulation on the floor of the attic which seals out any air movement between the living space and the attic. It also adds about R-4 insulation. It will not affect moisture levels in the attic. 

I would be thinking long and hard about the effective insulation and heating for the living space and whether a central furnace or going to radiant heating in areas would be a good move. This is where local expertise on the part of HVAC contractors is worth getting.


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