Hello everyone,
About two years ago, I bought an old house built in 1964 and completely renovated it. We moved in about 1.5 years ago. Now, I would like to insulate the ceiling of the top floor.
The roof consists of roof tiles, roofing felt, and wooden boarding – so it is completely uninsulated. Installing insulation between the rafters does not really make sense because I cannot convert the attic anyway. The height would only allow for a 1.4 m (4.6 ft) wide strip where you can stand upright. So unfortunately, that’s not really worthwhile.
My plan is to insulate the ceiling with 160 mm (6.3 inches) thick glass wool. A few very light items will still be stored up there, so I will lay down some wooden boards to stack the few light things on.
Cost-wise, this is the cheapest option, and I think it will make a noticeable difference in my old house.
What I don’t know is whether I need a vapor barrier or vapor retarder between the floor and the insulation. Can anyone tell me?
The ceiling is made of reinforced concrete, and there is even a few centimeters of screed on top. The apartment below has Heraklith boards on the underside. So, the layers from bottom to top are:
Plaster
Heraklith board (approx. 4 cm (1.6 inches))
Reinforced concrete slab
Screed
Then insulation with or without a vapor barrier/retarder in between.
My second question is: There is a door leading to the attic that opens inward. This means I cannot install insulation in the door’s swing area. Will this cause any problems?
So, hopefully someone can answer these two questions.
The total cost will be about 700€. I think (hope) this will definitely pay off within a few years.
Thanks in advance.
EDIT:
Oh yes, maybe one more small question: Does it make a big difference if I use 140 mm (5.5 inches) or 160 mm (6.3 inches) insulation? The extra cost would be about 70€.
Best regards,
Specki
About two years ago, I bought an old house built in 1964 and completely renovated it. We moved in about 1.5 years ago. Now, I would like to insulate the ceiling of the top floor.
The roof consists of roof tiles, roofing felt, and wooden boarding – so it is completely uninsulated. Installing insulation between the rafters does not really make sense because I cannot convert the attic anyway. The height would only allow for a 1.4 m (4.6 ft) wide strip where you can stand upright. So unfortunately, that’s not really worthwhile.
My plan is to insulate the ceiling with 160 mm (6.3 inches) thick glass wool. A few very light items will still be stored up there, so I will lay down some wooden boards to stack the few light things on.
Cost-wise, this is the cheapest option, and I think it will make a noticeable difference in my old house.
What I don’t know is whether I need a vapor barrier or vapor retarder between the floor and the insulation. Can anyone tell me?
The ceiling is made of reinforced concrete, and there is even a few centimeters of screed on top. The apartment below has Heraklith boards on the underside. So, the layers from bottom to top are:
Plaster
Heraklith board (approx. 4 cm (1.6 inches))
Reinforced concrete slab
Screed
Then insulation with or without a vapor barrier/retarder in between.
My second question is: There is a door leading to the attic that opens inward. This means I cannot install insulation in the door’s swing area. Will this cause any problems?
So, hopefully someone can answer these two questions.
The total cost will be about 700€. I think (hope) this will definitely pay off within a few years.
Thanks in advance.
EDIT:
Oh yes, maybe one more small question: Does it make a big difference if I use 140 mm (5.5 inches) or 160 mm (6.3 inches) insulation? The extra cost would be about 70€.
Best regards,
Specki
N
nightdancer19 Nov 2017 21:56Specki schrieb:
So you have 240 mm (9.4 inches), which I think is quite a lot.
Regards,
SpeckiI have 50 cm (20 inches); you can't insulate more cost-effectively.
N
nightdancer19 Nov 2017 22:01Specki schrieb:
Well, 50cm (20 inches) is too little for me.
I thought 160mm (6.3 inches) would be quite good. The question is simply how much more benefit you get if you increase it further... but that’s probably not easy to determine.50cm (20 inches), not 50mm (2 inches)
G
garfunkel20 Nov 2017 23:26Have you used the U-value calculator? It contains a lot of information; you can even calculate the payback period if you know the cost per m² (square meter), the heating period, costs for heat generation, and price increases.
In your case, maybe €7 per m² (square meter), based on an area of 100m² (1,076 square feet).
With that, you can probably use 160mm (6 inches) of insulation.
Plus the other ceiling layers as specified (except that I added 3cm (1 inch) of mineral wool under the screed because of the tool).
Heating for a warm apartment, from October to April.
10% price increase and 10 cents per kWh of heat.
This results in a payback period of 1.8 years.
With 140mm (5.5 inches) insulation, it’s also 1.8 years.
140mm insulation saves 35 kWh/m² (3.25 kWh/sq ft)
160mm saves 37 kWh/m² (3.44 kWh/sq ft)
200mm saves 39 kWh/m² (3.62 kWh/sq ft)
220mm saves 40 kWh/m² (3.72 kWh/sq ft)
500mm saves 45 kWh/m² (4.18 kWh/sq ft) with a payback period of 1.4 years.
These are rough estimates; if you can enter your planned setup exactly and know the data for the calculation, it’s quite easy to find out fairly accurately whether, when, and how much it pays off (potentially).
For a free tool, it’s an absolute recommendation that you should definitely check out for a project like this.
In your case, maybe €7 per m² (square meter), based on an area of 100m² (1,076 square feet).
With that, you can probably use 160mm (6 inches) of insulation.
Plus the other ceiling layers as specified (except that I added 3cm (1 inch) of mineral wool under the screed because of the tool).
Heating for a warm apartment, from October to April.
10% price increase and 10 cents per kWh of heat.
This results in a payback period of 1.8 years.
With 140mm (5.5 inches) insulation, it’s also 1.8 years.
140mm insulation saves 35 kWh/m² (3.25 kWh/sq ft)
160mm saves 37 kWh/m² (3.44 kWh/sq ft)
200mm saves 39 kWh/m² (3.62 kWh/sq ft)
220mm saves 40 kWh/m² (3.72 kWh/sq ft)
500mm saves 45 kWh/m² (4.18 kWh/sq ft) with a payback period of 1.4 years.
These are rough estimates; if you can enter your planned setup exactly and know the data for the calculation, it’s quite easy to find out fairly accurately whether, when, and how much it pays off (potentially).
For a free tool, it’s an absolute recommendation that you should definitely check out for a project like this.
I consider a payback period of 1.8 years or something similar to be unrealistic. Last year, we had a gas bill of about €1450 and used wood worth around €350, so a total of €1800.
It is a two-family house. Two apartments stacked one above the other, each a full floor with the same layout.
If I insulate the top ceiling now, it will probably only make a noticeable difference in the upper apartment (where I live).
The lower unit heats quite a bit more, so I estimate our heating costs at around €800.
If things go well, I might save between €100 and €150, which would already be something. That means the investment would pay off after about 5 to 7 years. I would be happy with that.
Yesterday, I ordered 180mm (7 inches) thick mineral wool insulation with a thermal conductivity of 0.035 W/mK.
A total of 105m² (1130 sq ft) for €740 including shipping.
Regards
Specki
It is a two-family house. Two apartments stacked one above the other, each a full floor with the same layout.
If I insulate the top ceiling now, it will probably only make a noticeable difference in the upper apartment (where I live).
The lower unit heats quite a bit more, so I estimate our heating costs at around €800.
If things go well, I might save between €100 and €150, which would already be something. That means the investment would pay off after about 5 to 7 years. I would be happy with that.
Yesterday, I ordered 180mm (7 inches) thick mineral wool insulation with a thermal conductivity of 0.035 W/mK.
A total of 105m² (1130 sq ft) for €740 including shipping.
Regards
Specki
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