ᐅ New Single-Family House Construction (KFW70) / Aerated Concrete vs. Sand-Lime Brick / Which Material to Choose?
Created on: 31 Jan 2014 08:27
L
Lacos
Hi everyone,
We are planning to build with a general contractor and have collected some offers. Some use aerated concrete, others use calcium silicate bricks. Some combine the two, using aerated concrete for the exterior walls and calcium silicate bricks on the inside.
What would you recommend? Is this combination of aerated concrete on the outside and calcium silicate bricks on the inside common and preferable?
Should we be concerned about cracks due to the different expansion properties of the two materials, or is this not an issue with proper construction?
What would you currently choose to build with or have built—what is your preferred building material?
Thank you in advance,
Lacos
We are planning to build with a general contractor and have collected some offers. Some use aerated concrete, others use calcium silicate bricks. Some combine the two, using aerated concrete for the exterior walls and calcium silicate bricks on the inside.
What would you recommend? Is this combination of aerated concrete on the outside and calcium silicate bricks on the inside common and preferable?
Should we be concerned about cracks due to the different expansion properties of the two materials, or is this not an issue with proper construction?
What would you currently choose to build with or have built—what is your preferred building material?
Thank you in advance,
Lacos
Hello everyone,
a quick question regarding the wall structure. The following has been discussed so far; is this acceptable from your point of view (KFW70):
0. Interior plaster layer
1. Calcium silicate brick: 17.5 cm (7 inches)
2. Insulation at least: 14.0 cm (5.5 inches)
3. Air gap
4. Brick veneer: 11.5 cm (4.5 inches)
The total wall thickness is supposed to be 46 cm (18 inches). What do you think? Is the insulation sufficient for a KFW70 single-family house? Or is it only adequate for KFW70 because it is "calculated favorably" with a ground source heat pump?
Best regards,
Lacos
a quick question regarding the wall structure. The following has been discussed so far; is this acceptable from your point of view (KFW70):
0. Interior plaster layer
1. Calcium silicate brick: 17.5 cm (7 inches)
2. Insulation at least: 14.0 cm (5.5 inches)
3. Air gap
4. Brick veneer: 11.5 cm (4.5 inches)
The total wall thickness is supposed to be 46 cm (18 inches). What do you think? Is the insulation sufficient for a KFW70 single-family house? Or is it only adequate for KFW70 because it is "calculated favorably" with a ground source heat pump?
Best regards,
Lacos
Hello,
[Quote="Lacos, post: 59281"].... Is the insulation sufficient for a KfW 70 single-family house? Or does it only meet KfW 70 standards because it is “optimistically calculated” with a ground source heat pump?...[ /QUOTE] This cannot be answered definitively in general terms, but the probability is very high! Possibly even significantly better! For example, if the building is close to KfW 55, it might be worth reconsidering. Sometimes it’s just minor details!
Especially with the insulation layer, the thermal conductivity value (WLS) is important, not just the thickness!
Here is a tip: Check the delivery note and document the respective labels to compare with the certification!
When it comes to the cavity wall, make sure that mortar residues do not block the air gap! Cover the rising masonry consistently against precipitation (both inner and outer leaf)!
The Energy Saving Ordinance and the KfW efficiency levels always depend on two parameters that must be met!
HT’ indicates the overall thermal quality of the building envelope (heat transmission losses).
qp’’ takes into account, in addition to HT’, the energy efficiency of the building services system!
“Optimistic calculations” occur whenever the schedule specified in the proofs is not followed by the subsequent planning, dimensioning, or implementation, for example of the system! This is not uncommon, but almost standard practice! Often, the building services system is not planned at all, or planned incorrectly, or assumptions are made.
In my opinion, this is not a suitable basis for a long-term investment decision.
You can see the effects in the image above.
If actual energy demand and supply do not align, the actual energy efficiency looks rather poor, especially with very sensitive heat generators like heat pumps!
Regards.
Lacos schrieb:Based on my experience and knowledge, you couldn’t have chosen a better wall construction. I believe you are generally in good hands on the construction side!
.... What do you think about it?...
[Quote="Lacos, post: 59281"].... Is the insulation sufficient for a KfW 70 single-family house? Or does it only meet KfW 70 standards because it is “optimistically calculated” with a ground source heat pump?...[ /QUOTE] This cannot be answered definitively in general terms, but the probability is very high! Possibly even significantly better! For example, if the building is close to KfW 55, it might be worth reconsidering. Sometimes it’s just minor details!
Especially with the insulation layer, the thermal conductivity value (WLS) is important, not just the thickness!
Here is a tip: Check the delivery note and document the respective labels to compare with the certification!
When it comes to the cavity wall, make sure that mortar residues do not block the air gap! Cover the rising masonry consistently against precipitation (both inner and outer leaf)!
The Energy Saving Ordinance and the KfW efficiency levels always depend on two parameters that must be met!
HT’ indicates the overall thermal quality of the building envelope (heat transmission losses).
qp’’ takes into account, in addition to HT’, the energy efficiency of the building services system!
“Optimistic calculations” occur whenever the schedule specified in the proofs is not followed by the subsequent planning, dimensioning, or implementation, for example of the system! This is not uncommon, but almost standard practice! Often, the building services system is not planned at all, or planned incorrectly, or assumptions are made.
In my opinion, this is not a suitable basis for a long-term investment decision.
You can see the effects in the image above.
If actual energy demand and supply do not align, the actual energy efficiency looks rather poor, especially with very sensitive heat generators like heat pumps!
Regards.
Lacos schrieb:
....(e.g., max. supply temperature of the underfloor heating <= 35°C (95°F)) etc.,... This refers to the overall system conditions! Different requirements/needs may exist for each room! => Room heating loads!Best regards
We are planning to construct the shell structure in a very similar way. Is it possible to estimate how much more expensive this is compared to a brick-faced shell with 25cm (10 inches) masonry bricks, insulation, and brick veneer (with roughly the same insulation values)?
Hello everyone,
The wall structure we have chosen is as follows:
- Gypsum plaster: 15mm (0.6 inches)
- Sand-lime brick: 150mm (6 inches)
- Mineral wool insulation, thermal conductivity grade 35: 160mm (6.3 inches)
- Air cavity (ventilated): 20mm (0.8 inches)
- Facing brick 1800: 115mm (4.5 inches)
= Total wall thickness 460mm (18 inches) // U-value should be between 0.18 - 0.19 W/(m²·K).
Is this a wall build that you would recommend, or is there room for improvement?
Regards and thanks,
Lacos
The wall structure we have chosen is as follows:
- Gypsum plaster: 15mm (0.6 inches)
- Sand-lime brick: 150mm (6 inches)
- Mineral wool insulation, thermal conductivity grade 35: 160mm (6.3 inches)
- Air cavity (ventilated): 20mm (0.8 inches)
- Facing brick 1800: 115mm (4.5 inches)
= Total wall thickness 460mm (18 inches) // U-value should be between 0.18 - 0.19 W/(m²·K).
Is this a wall build that you would recommend, or is there room for improvement?
Regards and thanks,
Lacos
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