ᐅ KfW 70 with gas-solar heating system

Created on: 17 Apr 2015 21:01
L
LittleWulf
Hello, we plan to start building our own home this year.

I already have two active discussion threads on this forum about it.

https://www.hausbau-forum.de/threads/Hausbau-kfw70-ca-150m-welche-Heizung-Gas-lwwp.12261/
https://www.hausbau-forum.de/threads/wir-wollen-bauen-ist-das-was-uns-angeboten-wird-so-i-o.12269/

We just got back from discussing the offer with the supplier.
I tried to talk about heating and ventilation; he shared his experiences, opinions, and advice.
This didn’t quite match what I had read so far, so now I’m uncertain and confused again.

We requested a 150m² (1,615 sq ft) solid house built to KFW 70 standard.

This is achieved through insulation and a gas-solar heating system. More details are in my other threads.

When I asked about a mechanical ventilation system with heat recovery, he said it’s not needed, that regular airing is sufficient.

He also said his son built a KFW 70 house with gas-solar three years ago and that he would never do that again. Better to build without KFW 70, save the money for the energy certificate inspection and the solar system (about 5,000), keep the insulation as is, and move on. Apparently, it’s not financially worthwhile.

Regarding the wall construction, another supplier told me the following:
Me: Is there an air gap between the insulation on the masonry and the facing brick?
He: Yes, of course, we don’t list that separately because it’s required by DIN (German industrial standards).

Today, with our current supplier:
Me: Is there an air gap between the insulation on the masonry and the facing brick?
He: No, that’s a cavity insulation. That might have been necessary in the past, but with today’s insulation materials, it’s no longer needed.

So what is correct? Is an air gap between the insulation and masonry required by DIN, or does it depend on which insulation material is used?
L
LittleWulf
17 Apr 2015 22:45
recoVair by Vaillant.
They seem to have only that one model. I found some information online under recoVair, but most of the time people mention other product names. On the manufacturer’s website, I only see that device and the technical data, of which I understand only about half. However, I can’t find any details about how it actually looks or is installed in a house anywhere :/
Mycraft17 Apr 2015 22:59
Well, it’s not just about the device—what kind of pipes and which valves? I think you should know that before making a purchase, right?

There are also different versions of the device... and the price difference can be as much as 1000 euros. So, which one will actually be installed?
Mycraft17 Apr 2015 23:06
here are some pictures:






Vaillant wall-mounted heating unit on the wall, visible exhaust pipes and piping below.



Attic with silver insulated ventilation ducts, wooden beams, and heating system.


You can see that quite different materials can be used with the same or similar device.
L
LittleWulf
18 Apr 2015 00:03
According to the manufacturer's website, there is only one device. However, that seems strange to me. That can’t be correct, can it?
Mycraft18 Apr 2015 08:03
No, that is not correct... There are different versions of the wall unit as well as an under-ceiling version.
B
Barossi
18 Apr 2015 08:14
Hello,
for KFW70 standard, ventilation is not necessarily required.

By the way: What is the approximate cost of an automatic ventilation system for a typical single-family house?

Best regards, Barossi