Hello,
even though similar questions have been asked here before, I am starting a new thread.
We are planning a new build and are currently comparing insulation options for the exterior walls, basement, roof, etc.
We want to build a solid structure with a double-shell masonry made of aerated concrete.
The construction companies all insulate the exterior walls with mineral wool at a thickness between 8 to 14 cm (3 to 6 inches), thermal conductivity value (WLG) 035.
For roof insulation, there is always a 20-24 cm (8 to 10 inches) insulation layer between the rafters with WLG 035. The attic space is insulated only if a finish is planned. If financially feasible, we would like to have this insulated as well.
Now the first question: can you recommend mineral wool insulation? And if yes, what thickness should be used and should one demand WLG 032 instead? Of course, better insulation is better, but what really makes sense when comparing initial investment costs to possible heating savings?
We also consulted a structural engineer who individually plans and supervises house constructions. He became quite concerned when looking at the specifications from the building companies. He recommends insulation with polyurethane boards having a thermal conductivity value (WLS) of 024 and a thickness of 20-24 cm (8 to 10 inches). For the roof, he recommends a full inboard insulation (above-rafter insulation) using the same material.
With this, our exterior wall would achieve a U-value of around 0.10-0.12 instead of possibly 0.16-0.18 with good mineral wool insulation (according to the information brochure).
Of course, this would be better, but his cost estimate showed that such a house would cost at least 50,000 € more and thus would no longer be financially feasible for us.
We really want to think this through carefully and do everything as properly and sensibly as possible and would be very grateful for professional answers!
Maya
even though similar questions have been asked here before, I am starting a new thread.
We are planning a new build and are currently comparing insulation options for the exterior walls, basement, roof, etc.
We want to build a solid structure with a double-shell masonry made of aerated concrete.
The construction companies all insulate the exterior walls with mineral wool at a thickness between 8 to 14 cm (3 to 6 inches), thermal conductivity value (WLG) 035.
For roof insulation, there is always a 20-24 cm (8 to 10 inches) insulation layer between the rafters with WLG 035. The attic space is insulated only if a finish is planned. If financially feasible, we would like to have this insulated as well.
Now the first question: can you recommend mineral wool insulation? And if yes, what thickness should be used and should one demand WLG 032 instead? Of course, better insulation is better, but what really makes sense when comparing initial investment costs to possible heating savings?
We also consulted a structural engineer who individually plans and supervises house constructions. He became quite concerned when looking at the specifications from the building companies. He recommends insulation with polyurethane boards having a thermal conductivity value (WLS) of 024 and a thickness of 20-24 cm (8 to 10 inches). For the roof, he recommends a full inboard insulation (above-rafter insulation) using the same material.
With this, our exterior wall would achieve a U-value of around 0.10-0.12 instead of possibly 0.16-0.18 with good mineral wool insulation (according to the information brochure).
Of course, this would be better, but his cost estimate showed that such a house would cost at least 50,000 € more and thus would no longer be financially feasible for us.
We really want to think this through carefully and do everything as properly and sensibly as possible and would be very grateful for professional answers!
Maya
B
Bauexperte9 Jun 2011 11:25Hello Maya,
What is your primary goal in building the house? Why does it have to be a cavity wall construction? Why use as much insulation as possible? What is your reasoning behind all of this?
Kind regards
Maya2011 schrieb:
We really want to think this through carefully and do everything as correctly and sensibly as possible, and we would be very, very grateful for professional answers!
What is your primary goal in building the house? Why does it have to be a cavity wall construction? Why use as much insulation as possible? What is your reasoning behind all of this?
Kind regards
Hello,
it is difficult to give a general recommendation on how you should insulate your house. The building must be considered as a whole system. This includes the construction technology (insulation of the building envelope) as well as the building services (heating, ventilation, etc.). Both must be coordinated and compatible to be cost-effective.
So definitely involve a planner. Ideally, an independent one who is not just trying to sell something because it is currently trendy.
Glue polyurethane boards to the exterior walls and then apply a cladding?
Expensive… expensive… expensive… and doesn’t really make sense. I don’t see any benefit in full insulation above the rafters.
Regards
it is difficult to give a general recommendation on how you should insulate your house. The building must be considered as a whole system. This includes the construction technology (insulation of the building envelope) as well as the building services (heating, ventilation, etc.). Both must be coordinated and compatible to be cost-effective.
So definitely involve a planner. Ideally, an independent one who is not just trying to sell something because it is currently trendy.
Maya2011 schrieb:
Then we also consulted a structural engineer who designs and supervises the construction of individual houses. He was overwhelmed by the specifications from the house building companies. He recommends insulation with polyurethane boards with a thermal conductivity value of 0.024 W/mK and a thickness of 20-24cm (8-10 inches).
Glue polyurethane boards to the exterior walls and then apply a cladding?
Maya2011 schrieb:
For the roof, he recommends full insulation above the rafters using the same material.
Expensive… expensive… expensive… and doesn’t really make sense. I don’t see any benefit in full insulation above the rafters.
Regards
Hello!
If it’s not affordable for you, then it’s off the table anyway. A good designer also distinguishes themselves by working within the budget set by the clients from the start.
On the topic: is the €50,000 extra cost only for the insulation, or is it the total additional cost for the custom-designed house?
I don’t know how large you want to build, etc… Do you already have an approximate idea of what energy demand you want to achieve?
Best regards,
Peter
Maya2011 schrieb:
Of course that would be better, but according to his estimate, the house would cost us at least €50,000 more, and that would no longer be affordable for us.
If it’s not affordable for you, then it’s off the table anyway. A good designer also distinguishes themselves by working within the budget set by the clients from the start.
On the topic: is the €50,000 extra cost only for the insulation, or is it the total additional cost for the custom-designed house?
I don’t know how large you want to build, etc… Do you already have an approximate idea of what energy demand you want to achieve?
Best regards,
Peter
Hello,
E.Curb has already explained: building, technical systems, climate location, and user behavior form a complex unit and should only be considered sensibly as a whole.
Best regards
Maya2011 schrieb:Long-term savings on heating costs can only be achieved sustainably through investments. The level of effort that is actually worthwhile can be determined with a cost-effectiveness analysis. It does not always have to be a certified Passive House. One thing is certain: the prices of all energy sources will rise significantly in the future. The best energy is always the energy that is not needed—that is, reducing demand!
...Of course, better insulation is better. But what really makes sense when comparing investment costs to possible heating savings?
E.Curb has already explained: building, technical systems, climate location, and user behavior form a complex unit and should only be considered sensibly as a whole.
Best regards
Hello
and many thanks for the initial responses.
I will respond as best as I can:
We are planning a house with around 150 m2 (1,615 sq ft) plus a basement.
Heating system: gas condensing boiler plus solar for water and heating, water-bearing stove, underfloor heating, controlled ventilation system with heat recovery.
The goal of our insulation is to keep energy consumption low and avoid mold growth caused by thermal bridges, etc. Overall, a solid house with a good balance between insulation and heating systems.
So you find the polyurethane insulation on the roof not very sensible?
But isn’t external roof insulation (above the rafters) better than insulation between rafters? What are the possible advantages and disadvantages?
Yes, the polyurethane boards are planned to be installed on the exterior wall, where mineral wool and a brick veneer will otherwise be placed.
This mentioned structural engineer also uses this type of roof insulation for house renovations. Would it be more appropriate in that context or not? (Some acquaintances might renovate with him).
The 50,000 is already considered the total cost, but the house won’t really look different or better than one from a building contractor and will also be smaller.
For the technology and equipment, we have specified the same details there.
He estimated the cost for a brick-clad pointed roof dormer, which we like (I know, not energy-efficient, but it should also look good, right?), at a minimum of €9,000.
I look forward to your feedback...
and many thanks for the initial responses.
I will respond as best as I can:
We are planning a house with around 150 m2 (1,615 sq ft) plus a basement.
Heating system: gas condensing boiler plus solar for water and heating, water-bearing stove, underfloor heating, controlled ventilation system with heat recovery.
The goal of our insulation is to keep energy consumption low and avoid mold growth caused by thermal bridges, etc. Overall, a solid house with a good balance between insulation and heating systems.
So you find the polyurethane insulation on the roof not very sensible?
But isn’t external roof insulation (above the rafters) better than insulation between rafters? What are the possible advantages and disadvantages?
Yes, the polyurethane boards are planned to be installed on the exterior wall, where mineral wool and a brick veneer will otherwise be placed.
This mentioned structural engineer also uses this type of roof insulation for house renovations. Would it be more appropriate in that context or not? (Some acquaintances might renovate with him).
The 50,000 is already considered the total cost, but the house won’t really look different or better than one from a building contractor and will also be smaller.
For the technology and equipment, we have specified the same details there.
He estimated the cost for a brick-clad pointed roof dormer, which we like (I know, not energy-efficient, but it should also look good, right?), at a minimum of €9,000.
I look forward to your feedback...
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