ᐅ Reinforce insulation of the ceiling between floors to reduce heat transfer to the upper floor.
Created on: 8 Mar 2021 13:18
A
andimann
Hello everyone,
We built our house in 2016, and the floor/ceiling construction between the upper floor and the attic is as follows:
This assembly achieves a U-value of about 0.234. The attic is therefore an unheated roof space. Not a fully conventional cold roof, since there is also a vapor-permeable underlay membrane beneath the roof tiles, but close to it.
This U-value is clearly worse than the U-value of the walls on the upper floor (about 0.15), but so far everything is fine: no moisture issues, and adding more insulation would hardly pay off in terms of heating costs.
However, in extreme cases the upper floor can reach temperatures up to 26°C (79°F) in summer, and we have considered installing air conditioning. We will likely do this, but only on the ground floor, as it would be a huge construction effort on the upper floor.
A rough estimate shows that about two-thirds of the heat gain into the upper floor in summer comes through the ceiling from the attic. This is due to the approximately 92 m² (990 ft²) of surface area and the temperatures above 55°C (131°F) up there. (At 55°C, the LCD thermometer display turned black, so it may well get even hotter.)
The plan is now to reduce the heat transfer from the attic to the upper floor by improving the insulation. An additional 120 mm (4.7 inches) of EPS 035 insulation is planned, resulting in the following total assembly:
This should produce a U-value of 0.130 for the ceiling. This lowers the heat flow from the attic to the upper floor from about 650 watts to 350 watts, which accounts for approximately 30% of the total heat gain.
I hope this will slow down the temperature rise on the upper floor and reduce the maximum temperature from 26°C (79°F) to 25°C (77°F) or better, 24°C (75°F).
Question: Could this work, or am I missing something fundamental?
Thanks and best regards,
Andreas
We built our house in 2016, and the floor/ceiling construction between the upper floor and the attic is as follows:
- 180 mm (7 inches) concrete
- PE foil as a vapor barrier
- 160 mm (6.3 inches) EPS 040 insulation
This assembly achieves a U-value of about 0.234. The attic is therefore an unheated roof space. Not a fully conventional cold roof, since there is also a vapor-permeable underlay membrane beneath the roof tiles, but close to it.
This U-value is clearly worse than the U-value of the walls on the upper floor (about 0.15), but so far everything is fine: no moisture issues, and adding more insulation would hardly pay off in terms of heating costs.
However, in extreme cases the upper floor can reach temperatures up to 26°C (79°F) in summer, and we have considered installing air conditioning. We will likely do this, but only on the ground floor, as it would be a huge construction effort on the upper floor.
A rough estimate shows that about two-thirds of the heat gain into the upper floor in summer comes through the ceiling from the attic. This is due to the approximately 92 m² (990 ft²) of surface area and the temperatures above 55°C (131°F) up there. (At 55°C, the LCD thermometer display turned black, so it may well get even hotter.)
The plan is now to reduce the heat transfer from the attic to the upper floor by improving the insulation. An additional 120 mm (4.7 inches) of EPS 035 insulation is planned, resulting in the following total assembly:
- 180 mm (7 inches) concrete
- PE foil as a vapor barrier
- 160 mm (6.3 inches) EPS 040
- 120 mm (4.7 inches) EPS 035
This should produce a U-value of 0.130 for the ceiling. This lowers the heat flow from the attic to the upper floor from about 650 watts to 350 watts, which accounts for approximately 30% of the total heat gain.
I hope this will slow down the temperature rise on the upper floor and reduce the maximum temperature from 26°C (79°F) to 25°C (77°F) or better, 24°C (75°F).
Question: Could this work, or am I missing something fundamental?
Thanks and best regards,
Andreas
P
pagoni20208 Mar 2021 22:23We might soon face a similar question. For now, we hope that we can manage without air conditioning... we’ll see.
@andimann
No matter which U-values you add up or compare,
outside it’s hot, around 35°C (95°F) during the day and barely cooler at night,
the house heats up and can’t get rid of the heat, only by bringing in cooling power with an air conditioner will it cool down.
The Mediterranean-style construction is not an option for the window areas,
so it’s California-style construction, lots of glass and air conditioning.
Often, running the system at low capacity is enough to make it comfortable.
And as you said, heat rises, so one air conditioner in the bedroom and one in the open living area, at minimum.
No matter which U-values you add up or compare,
outside it’s hot, around 35°C (95°F) during the day and barely cooler at night,
the house heats up and can’t get rid of the heat, only by bringing in cooling power with an air conditioner will it cool down.
The Mediterranean-style construction is not an option for the window areas,
so it’s California-style construction, lots of glass and air conditioning.
Often, running the system at low capacity is enough to make it comfortable.
And as you said, heat rises, so one air conditioner in the bedroom and one in the open living area, at minimum.
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