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1967 R50/2
Hot Roof Insulation on a Stone House

Hello All-

I have a very particular question:

1. We have an old 1 story stone home. Construction is load bearing 12in thick stone walls with 2X4 construction on the inside which back plaster walls and provide the route for electrical wires etc.

2. As I said, stone walls are load bearing and the hip roof joises rests on them. In otherwords, the stone runs right up to the roof.

3. At some time in the distant past, the attic space was partly converted into rooms with two dormers on either side of the collar ties. Possibly maid quarters? I don't know, but subsequent owners have completely updated the space into rather nice bedrooms. Teh downside of this is that the true unfinished attic space has been chopped up into 4 parts: A.front north, B. front south, C. Back, and D. top above the collar ties. There is no real circulation between hese parts as the living space sits between them.

4. There is a front dormer vent that sits between A and B and another one in C.

5. There are also thermostatically controlled exhaust fans in C. and D.

6. There is no soffit venting, ridge vents or such.

7. There is some fiberglass batting on the walls of the living space. But, the only other insulation is on the attic floor and consists of maybe 2in of wool. Which is completely inadequate for our climate.

So here is the problem, that even with the vents, fans and insulation, the living space which is insulated with old Fiberglass batting is basically unliveable. Too hot in the summer and too cold in the winter. The downstairs is none to warm either.

8. We'd like to change this. I had an insulation expert come in to look and what he suggested was to blow in Hot Roof insulation against the joists sealing up the two dormer vents and thermostatically controlled fans. In theory this would insulate the entire attic space from cold and heat, and thereby bringing the living space in equilibrium fromt he rest of the house.

So here is my question: I am concerned that if the attic is hermetically sealed like this the moisture in the house will have no place to go as the ground floor is defacto sealed by 12in of stone.

Any opinions on this? Anyone put a hot roof system into a stone home? Am I being overly concerned about the moisture? Anyone see any other soluition besides a hot roof?

canuk
Re: Hot Roof Insulation on a Stone House
1967 R50/2 wrote:

Hello All-

I have a very particular question:

1. We have an old 1 story stone home. Construction is load bearing 12in thick stone walls with 2X4 construction on the inside which back plaster walls and provide the route for electrical wires etc.

2. As I said, stone walls are load bearing and the hip roof joises rests on them. In otherwords, the stone runs right up to the roof.

3. At some time in the distant past, the attic space was partly converted into rooms with two dormers on either side of the collar ties. Possibly maid quarters? I don't know, but subsequent owners have completely updated the space into rather nice bedrooms. Teh downside of this is that the true unfinished attic space has been chopped up into 4 parts: A.front north, B. front south, C. Back, and D. top above the collar ties. There is no real circulation between hese parts as the living space sits between them.

4. There is a front dormer vent that sits between A and B and another one in C.

5. There are also thermostatically controlled exhaust fans in C. and D.

6. There is no soffit venting, ridge vents or such.

7. There is some fiberglass batting on the walls of the living space. But, the only other insulation is on the attic floor and consists of maybe 2in of wool. Which is completely inadequate for our climate.

So here is the problem, that even with the vents, fans and insulation, the living space which is insulated with old Fiberglass batting is basically unliveable. Too hot in the summer and too cold in the winter. The downstairs is none to warm either.

8. We'd like to change this. I had an insulation expert come in to look and what he suggested was to blow in Hot Roof insulation against the joists sealing up the two dormer vents and thermostatically controlled fans. In theory this would insulate the entire attic space from cold and heat, and thereby bringing the living space in equilibrium fromt he rest of the house.

So here is my question: I am concerned that if the attic is hermetically sealed like this the moisture in the house will have no place to go as the ground floor is defacto sealed by 12in of stone.

Any opinions on this? Anyone put a hot roof system into a stone home? Am I being overly concerned about the moisture? Anyone see any other soluition besides a hot roof?

What is proposed is a modern way of insulating the attic spaces.
By insulating all the exterior surfaces and eliminating the venting of the attic you are directly reducing the heat gain/loss within that space and subsequently reducing the heat gain/loss for the living space --- a positive benefit.

Generally the moisture comes from warm humid outside air and within the living space from day to day activites-- cooking , showers , cleaning , etc..

Moisture generally originates from vapour and the mechanisim known as vapour drive is one of the common ways moisture transfers from the living space into attic or from the attic to the living space.

Much like the basic laws of thermal dynamics -- heat travels to cold ( simply put )
so does vapour drive .

In the colder winter when the living space is being heated and a vented attic space is at the same temperature of the outside. Because of this difference in temperature is why you will have heat loss. The closer the two spaces are in temperature the less heat loss.
The same is true during the summer when you are cooling the inside living space --- just in reverse. The heat from outside is trying to get in producing heat gain.

The same holds true with the vapour drive. During the cold winter the warmed inside moisture laden air will be driven into the cold vented attic space and condense once it contacts the colder attic. The opposite occurs during the warm summer when hot outside air is driving inward.

Regardless of the fact your home is contructed of stone , making the living space more air tight will have an effect of increasing of the inside humidity ( moisture ).

Up here we have been using Heat Recovery Ventilators ( HRV ) which are also being referred to as Energy Recovery Ventilators ( ERV ) for a quite of number of years now --- google them to learn more.

These devices are pretty much standard to greatly reduce moisture issues as well as improving inside air quality and is something I recommend looking into.

Hopefully this helps. :)

1967 R50/2
Re: Hot Roof Insulation on a Stone House

So in short you are saying: "Yes, moisture could become a problem".

my concern was that this would be the case in winter. The moist interior air, when deprived of attic venting, would condence against the cold stone walls.

I googled the heat exchanger...Thanks for that bit of info. However, I really see no way to implement that through the entire house.

So, I'll throw it back out there with a slightly more general focus: has anyone equipped their older home with a Hot Roof as discussed above? If yes...why and what were the results. If not, why not? and what did you do instead.

canuk
Re: Hot Roof Insulation on a Stone House
1967 R50/2 wrote:

So in short you are saying: "Yes, moisture could become a problem".
Sort of yes --- It's not confined to *hot roof* insulated homes. Any home that you change the dynamics of has a chance of increased humidity. Sealing gaps , changing out HVAC equipment to direct vent , not having bathroom exhaust vents , etc. will all contribute to increased humidity.
That's why it's important to controll the interior humidty.

my concern was that this would be the case in winter. The moist interior air, when deprived of attic venting, would condence against the cold stone walls.
As I said earlier --- all exterior surfaces in the attic need to be insulated.
The stone part of the wall inside the attic should also be coated with the insulation -- not just the underside of the roof.

I googled the heat exchanger...Thanks for that bit of info. However, I really see no way to implement that through the entire house.
I have no idea as to what type of heating/cooling system exists but a HRV can even be installed in homes with hot water heating.

So, I'll throw it back out there with a slightly more general focus: has anyone equipped their older home with a Hot Roof as discussed above? If yes...why and what were the results. If not, why not? and what did you do instead.

This type of system has been done for some time now and becoming more popular around these parts. When done correctly there are no issues. Once I'm finished with my own renovations this is the way I will go.

1967 R50/2
Re: Hot Roof Insulation on a Stone House

Actually, the whole point is rather moot.

The contractor just gave an estimate this morning for his hot roof, and not only is it not affordable, I think there is no way it could possibly ever break-even, not in the short term, and also not in the medium or long term...even if it cut the heating and cooling bill by 100%, which of course would be impossible.

However I think you missed my point about the walls. The stone walls extend up to the attic but not in the attic. Remember there are wooden walls inside the stone walls. If these are capped by a "Hot Roof" impermeable layer, and surrounded by an impermeable stone layer, than the air inside them has nowhere to migrate to and the moisture will condense in the walls...against the cold stone.

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