ᐅ Perimeter insulation / slab insulation / brick width / window
Created on: 10 Feb 2018 11:15
S
Stagenberger
I have received a proposal from a well-known developer company in a neighboring town. For budget reasons, I asked them to calculate the cost of the most affordable house that complies with the current energy saving regulations but does not have to meet KfW 55 standards or better. They prepared their calculation based on my specifications. I then gave the offer to an acquaintance who works in construction planning and project supervision and also collaborates with other building companies.
He also provided me with a cost estimate for handling the project himself.
His main criticisms:
- The developer uses only 30 cm (12 inches) Ytong blocks with a thermal conductivity (λ-value) of 0.09, whereas my acquaintance believes it should definitely be 36.5 cm (14 inches) Ytong blocks with a λ-value of 0.08.
- The developer included only 5 cm (2 inches) of perimeter insulation in the basement walls, but my acquaintance recommends at least 10 to 12 cm (4 to 5 inches).
- Basement windows have a U-value of 0.7, while he recommends 0.5.
- The foundation slab is insulated with only 50 mm (2 inches) of insulation, but it should be 100 mm (4 inches).
How would you assess this here?
He also provided me with a cost estimate for handling the project himself.
His main criticisms:
- The developer uses only 30 cm (12 inches) Ytong blocks with a thermal conductivity (λ-value) of 0.09, whereas my acquaintance believes it should definitely be 36.5 cm (14 inches) Ytong blocks with a λ-value of 0.08.
- The developer included only 5 cm (2 inches) of perimeter insulation in the basement walls, but my acquaintance recommends at least 10 to 12 cm (4 to 5 inches).
- Basement windows have a U-value of 0.7, while he recommends 0.5.
- The foundation slab is insulated with only 50 mm (2 inches) of insulation, but it should be 100 mm (4 inches).
How would you assess this here?
Well, to put it bluntly... take nordlys' example. €800 gas for, I believe, a 110m² (1,184 sq ft) bungalow? We are estimating €500-600 electricity (geothermal) for about 195m² (2,099 sq ft). Thanks to the insulation, we save significantly on the sizing of the heat pump and the depth of the drilling—thousands of euros. But if you’re going with gas anyway, which is fine, it doesn’t matter because those systems can produce far more heat than needed. It’s also a question of the overall concept and what makes sense.
Ultimately, time will tell what happens with energy prices in the future. If you can’t afford the investment now, that’s just the reality and a personal priority. Everyone has to make that decision themselves. It might be more expensive later, but no one knows for sure. Those who use little energy won’t have a big issue with price increases.
Besides cost-effectiveness, there can be other factors. A basement with 5cm (2 inches) of perimeter insulation probably won’t be heated and won’t be suitable for heating later, so it will be useful mostly for storage—like storing potatoes (which, by the way, is quite an expensive use of a basement—just think about that). You need to know what you want. Better insulated glazing is also more comfortable when you’re sitting in a chair and feel the glass behind you. Some budget-conscious people have ventilation openings installed in window frames to let cold fresh air in. Maybe these aren’t big issues, but others want to avoid them and expect new builds to offer more comfort than 20-year-old existing homes. This also affects resale value.
If the budget is tight now, I would put the investment into the building fabric and possibly upgrade the fittings later. For example, if a fireplace is planned, I would cancel it immediately to improve the house’s energy performance. Just as an example.
Ultimately, time will tell what happens with energy prices in the future. If you can’t afford the investment now, that’s just the reality and a personal priority. Everyone has to make that decision themselves. It might be more expensive later, but no one knows for sure. Those who use little energy won’t have a big issue with price increases.
Besides cost-effectiveness, there can be other factors. A basement with 5cm (2 inches) of perimeter insulation probably won’t be heated and won’t be suitable for heating later, so it will be useful mostly for storage—like storing potatoes (which, by the way, is quite an expensive use of a basement—just think about that). You need to know what you want. Better insulated glazing is also more comfortable when you’re sitting in a chair and feel the glass behind you. Some budget-conscious people have ventilation openings installed in window frames to let cold fresh air in. Maybe these aren’t big issues, but others want to avoid them and expect new builds to offer more comfort than 20-year-old existing homes. This also affects resale value.
If the budget is tight now, I would put the investment into the building fabric and possibly upgrade the fittings later. For example, if a fireplace is planned, I would cancel it immediately to improve the house’s energy performance. Just as an example.
S
Stagenberger10 Feb 2018 14:24Alex85 schrieb:
A basement with 5cm (2 inches) of perimeter insulation is probably not heated and later won’t be effectively heatable, making it mainly useful for storing potatoes (by the way, quite a lot of money for a basement just for potato storage – think about that). Except for the utility room in the basement, all rooms will have underfloor heating. From this perspective, would a better perimeter insulation be advisable?
Alex85 schrieb:
We expect electricity costs of 500-600€ for geothermal heating for around 195 square meters (2100 square feet). Thanks to the insulation, we save significantly on the size of the heat pump and the depth of the borehole. Thousands of euros. Since I am also planning a new build with about 190 square meters (2045 square feet) and geothermal heating, I would be interested in more detailed numbers. That means, roughly how much do you save specifically, compared to which type of insulation, and what insulation do you have now?
Thanks in advance.
Search for this in the forum; there have already been several threads where people have shared their consumption data.
Otherwise, you can also find a heat pump database with this kind of information via Google.
We are building to KFW 55 standard, with a heating load of 5.5 kW compared to about 7.5 kW if built only according to the energy saving regulation. This saves roughly €1000 on the smaller heat pump and about €2000 on the shallower borehole.
Otherwise, you can also find a heat pump database with this kind of information via Google.
We are building to KFW 55 standard, with a heating load of 5.5 kW compared to about 7.5 kW if built only according to the energy saving regulation. This saves roughly €1000 on the smaller heat pump and about €2000 on the shallower borehole.
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