ᐅ Aerated concrete exterior wall vs. energy efficiency regulations
Created on: 28 Jun 2015 20:07
T
tecker2010
Hi,
I hope this topic hasn’t been asked before; otherwise, I must admit I didn’t use the search function thoroughly enough.
We are planning to build a single-family house and are currently in the preparation phase. The plan is for a townhouse-style villa (2 full floors) with 150m2 (1,615 sq ft). Right now, I’m looking into exterior walls, energy-saving regulations, etc., and I’ve come across some fundamental questions—or rather, several.
According to our builder, standard exterior walls will be made of aerated concrete blocks (brand Ytong) with a thickness of 24cm (9.5 inches) without any additional insulation or external thermal insulation composite system (ETICS). Assuming the blocks used have a thermal conductivity of 0.09 W/(m·K) (there are different blocks ranging from 0.07 to 0.18), my rough calculations lead to a U-value of 0.37 W/(m²·K), or about 0.3 W/(m²·K) if we opt for 30cm (12 inches) thick walls. In terms of energy efficiency and future-oriented building, this is obviously insufficient.
I’ve read that according to the 2009 Energy Saving Ordinance (EnEV), exterior walls are allowed a maximum U-value of 0.28 W/(m²·K).
My specific questions are: Is this a regulation the builder is legally required to follow? What wall thickness would you recommend? Also, is what I’ve described correct?
I’m hearing different opinions, ranging from “Go for a 36cm (14 inches) wall thickness because of better insulation” (from someone who has built twice) to “I’d choose 24cm (9.5 inches) so the house can breathe and put enough solar panels on the roof for self-consumption” (an architect).
Thanks a lot for your feedback!
Sebastian
I hope this topic hasn’t been asked before; otherwise, I must admit I didn’t use the search function thoroughly enough.
We are planning to build a single-family house and are currently in the preparation phase. The plan is for a townhouse-style villa (2 full floors) with 150m2 (1,615 sq ft). Right now, I’m looking into exterior walls, energy-saving regulations, etc., and I’ve come across some fundamental questions—or rather, several.
According to our builder, standard exterior walls will be made of aerated concrete blocks (brand Ytong) with a thickness of 24cm (9.5 inches) without any additional insulation or external thermal insulation composite system (ETICS). Assuming the blocks used have a thermal conductivity of 0.09 W/(m·K) (there are different blocks ranging from 0.07 to 0.18), my rough calculations lead to a U-value of 0.37 W/(m²·K), or about 0.3 W/(m²·K) if we opt for 30cm (12 inches) thick walls. In terms of energy efficiency and future-oriented building, this is obviously insufficient.
I’ve read that according to the 2009 Energy Saving Ordinance (EnEV), exterior walls are allowed a maximum U-value of 0.28 W/(m²·K).
My specific questions are: Is this a regulation the builder is legally required to follow? What wall thickness would you recommend? Also, is what I’ve described correct?
I’m hearing different opinions, ranging from “Go for a 36cm (14 inches) wall thickness because of better insulation” (from someone who has built twice) to “I’d choose 24cm (9.5 inches) so the house can breathe and put enough solar panels on the roof for self-consumption” (an architect).
Thanks a lot for your feedback!
Sebastian
They don’t build pure 24cm (9.5 inches) aerated concrete... it’s either a cavity wall or external thermal insulation composite system (ETICS)... and that will be the case with your residential building too – there’s virtually no other way. Regarding the structural engineering, I can only agree with oleda.
EveundGerd23 Jan 2016 20:11A 24cm (9.5 inches) Ytong wall without external thermal insulation composite system (ETICS) definitely no longer complies with current energy-saving regulations.
A simple 24cm (9.5 inches) Ytong wall structure combined with triple glazing is not compatible. The masonry must be coordinated with the windows and vice versa; otherwise, moisture will condense on the walls.
The architect’s statement is questionable.
A simple 24cm (9.5 inches) Ytong wall structure combined with triple glazing is not compatible. The masonry must be coordinated with the windows and vice versa; otherwise, moisture will condense on the walls.
The architect’s statement is questionable.
I’ve encountered something similar... We had an architect who said that a mechanical ventilation system wasn’t necessary because the house “breathes.” At first, I thought he was a bit crazy. But then we visited several of his projects and spoke with the homeowners – they really didn’t have any air quality issues. A lot of wood, lime plaster, and clay plaster were used in the construction.
He also mentioned one detail – the windows are not foam insulated but sealed with jute (?)
At the end, we asked about heating costs:
House built in 2005, 180 sqm (15 cm (6 inches) Perlite insulation ~0.22 W/m²K, 20 cm (8 inches) cellulose insulation in the roof ~0.19 W/m²K) -> 1800 € heating costs per year.
House built in 2006, 110 sqm (15 cm (6 inches) Perlite insulation ~0.22 W/m²K, 20 cm (8 inches) cellulose insulation in the roof ~0.19 W/m²K) -> 1200 € heating costs per year.
User behavior aside... the heating costs – gas – do tell you something about the “breathing.” Either the occupants ventilate a lot or there is air leakage... (don’t get me wrong – the houses were beautiful and unique).
He also mentioned one detail – the windows are not foam insulated but sealed with jute (?)
At the end, we asked about heating costs:
House built in 2005, 180 sqm (15 cm (6 inches) Perlite insulation ~0.22 W/m²K, 20 cm (8 inches) cellulose insulation in the roof ~0.19 W/m²K) -> 1800 € heating costs per year.
House built in 2006, 110 sqm (15 cm (6 inches) Perlite insulation ~0.22 W/m²K, 20 cm (8 inches) cellulose insulation in the roof ~0.19 W/m²K) -> 1200 € heating costs per year.
User behavior aside... the heating costs – gas – do tell you something about the “breathing.” Either the occupants ventilate a lot or there is air leakage... (don’t get me wrong – the houses were beautiful and unique).
EveundGerd23 Jan 2016 21:41These heating costs were achieved with double glazing from 1975, aluminum frames without insulation in the frame, and 30cm (12 inches) pumice blocks without external thermal insulation composite system (ETICS) on 240 sqm (2583 sq ft). An old building with a partial basement built into a slope from 1964. However, this does not include hot water. But keep in mind, it is an uninsulated old building! It was also built individually.
What is the reason for using 24cm (9.5 inches) aerated concrete walls? The additional cost compared to 36cm (14 inches) walls shouldn’t be too high, but the insulation value is significantly better. I have also never heard of houses being built with 24cm (9.5 inches) aerated concrete.
I myself will be building with 36cm (14 inches) aerated concrete walls. I even considered 42cm (16.5 inches) walls at one point...
I myself will be building with 36cm (14 inches) aerated concrete walls. I even considered 42cm (16.5 inches) walls at one point...
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