Passiv house costs.

[garrymartin]

38 minutes ago, -rick- said:

A lot of custom one-off homes will tend to be in the more expensive as the customers will want nice things like big windows, overhangs, lots of corners and detail or simply to squeeze a lot into a difficult site. Meeting the passivhaus standards then will add a lot more cost than a simple box.

Spot on. Passivhaus is only of near-equal cost parity if the building was designed to be Passivhaus from the beginning, including principles of form factor. If someone has designed a home, and then tries to make it Passivhaus, then you are almost in retrofit territory, which of course costs more.

 

18 minutes ago, saveasteading said:

I was thinking of one-offs as most on BH are.

I think you can do one-offs too at significantly less than 30% increase in costs, but as above, you need to design from the outset.

 

The garage door is a great example earlier in this thread. It looks like the architect/designer didn't consider this at the outset, and possibly made the fire *and* airtightness barrier/boundary the same, causing the requirement for an airtight and thermally efficient fire door, which was very costly. Separating those elements (fire/airtight) at the design stage may have resulted in signficantly less cost. It may not have been possible given site or design constraints, but just one example.

[Gone West]

3 hours ago, -rick- said:

An example of cost saving might be that if you meet passivehaus standards, especially in a compact home, your heating demands are tiny so you can skip the expensive heat pump install and just put in a couple of small electric heaters.

Exactly. We designed and built our last place to PH standards. It was around 130m2 and was heated with a towel rail in each of the three bathrooms and an EASHP built into the MVHR came on when the weather was very cold. The whole house was kept at 23C 24/7. Very low energy costs.

Edited yesterday at 12:11 by Gone West

[MPx]

14 hours ago, Oz07 said:

I've been thinking about this. Not an ideal solution but one which should pass? Have a non fd rated passiv level insulated door opening into your hallway, and a fire doorset immediately behind opening into the garage. Depending what is stored in the garage after sign off you may want to remove fd? If the garage size and position of opening allows you may even like to build a small stud lobby within the garages. Insulated door into house, fire line the stud and fire door on the stud going into garage?

Yes, as our walls will be some 400mm thick we could support a double door withing the aperture and we considered the FD on the garage side and the passive door in the hall, but what a pain to use, exacerbated by the self close on the fire door.  

 

12 hours ago, -rick- said:

 

The problem you describe here is one that has come up several times on this forum (for people who are just trying to be energy efficient, not building to passivhaus standards). Integrated garages impose a lot of extra costs that aren't obvious when the architect first draws them. That said, they are often the only option in many plots.

Integral garage a part of our brief.  Drive in and enter the house out of the weather.  

 

So part of the design.  But as it doesn't appear to be possible to make an operational garage airtight or thermally efficient it has to be outside the envelope.

 

Building control also working against us.  Nonsense requirement to have a 150mm step between garage and hall - no doubt mitigating risks that no-one has ever seen materialise.  Working opposite to the requirement to have a level entry to the front door.  By definition there must be a step or slope if the garage is 150mm lower so "level" is not a possible outcome.  We're just trying to make sure we're able to manage life with mobility issues should that come to pass - but hopefully it wont!

Edited 19 hours ago by MPx

[Oz07]

8 hours ago, MPx said:

Yes, as our walls will be some 400mm thick we could support a double door withing the aperture and we considered the FD on the garage side and the passive door in the hall, but what a pain to use, exacerbated by the self close on the fire door.  

 

Integral garage a part of our brief.  Drive in and enter the house out of the weather.  

 

So part of the design.  But as it doesn't appear to be possible to make an operational garage airtight or thermally efficient it has to be outside the envelope.

 

Building control also working against us.  Nonsense requirement to have a 150mm step between garage and hall - no doubt mitigating risks that no-one has ever seen materialise.  Working opposite to the requirement to have a level entry to the front door.  By definition there must be a step or slope if the garage is 150mm lower so "level" is not a possible outcome.  We're just trying to make sure we're able to manage life with mobility issues should that come to pass - but hopefully it wont!

I think I'd go for the double door then consider ripping one out. Does a fire door need a closer on if you have a "fire door keep locked" sign on instead?

[saveasteading]

9 hours ago, MPx said:

Building control also working against us. 

Can you ask them to show you the "regulation" that requires this, or to explain the reasoning?

 

1 hour ago, Oz07 said:

double door then consider ripping one out. Does a fire door need a closer on if you have a "fire door keep locked" sign

This "threat" can make a bco accept a sensible compromise. Nobody likes to look stupid. Maybe they personally agree with you but are misinterpreting the rules. 

Or switch them later.

Door 1 to comply with building regs.

Door 2 for passive.

 

Or invent your own door which foes both jobs.... somehow.

 

Yes it needs a closer.

[garrymartin]

1 hour ago, saveasteading said:

Can you ask them to show you the "regulation" that requires this, or to explain the reasoning?

It's in Part B somewhere, but I think it's 100mm not 150mm. You can also meet the requirement by having the floor slope away from the threshold, so it isn't mandatory. It's something to do with preventing diesel/petrol spills migrating from the garage into the house.

 

EDIT - I decided to find it... Section 5.7

 

[-rick-]

21 minutes ago, garrymartin said:

It's in Part B somewhere, but I think it's 100mm not 150mm. You can also meet the requirement by having the floor slope away from the threshold, so it isn't mandatory. It's something to do with preventing diesel/petrol spills migrating from the garage into the house.

 

EDIT - I decided to find it... Section 5.7

 

Beat me to it!

 

For as long as petrol cars are common it seems like a sensible rule. Fuel leaking into the ground floor is both a huge issue to clean up and in the event of fire likely blocks the exit and causes rapid spread. Having said that, this is one of the reasons my preference would be for a garage that is not part of the house if there is space (can always put a covered/weather protected walkway in between them).

 

Hopefully will get removed once EVs take over.

Edited 7 hours ago by -rick-

[saveasteading]

The whole floor could slope away from the door, perhaps with a small lip at the door. I wonder if it is supposed to allow for a whole tank. I've so ig could bd allowed to drain understand garage door. Or to have no draughts, build a sump into the floor.

[-rick-]

36 minutes ago, saveasteading said:

The whole floor could slope away from the door, perhaps with a small lip at the door. I wonder if it is supposed to allow for a whole tank. I've so ig could bd allowed to drain understand garage door. Or to have no draughts, build a sump into the floor.

 

That's my understanding. Admittedly there are less rusting out cars around these days and modern cars are less likely to dump the tank but the risk is still there and I doubt we'll see any change until petrol is something you have to actively seek out vs popping to the local petrol station.

[saveasteading]

sorry about the spelling collapse. 

 

If so, then it could be allowed to drain under the garage door.

 

The sump would be a neater and more technical answer but I guess carries more risk, although the smell should be apparent.

 

New cars have plastic fuel tanks.  This allows car park fires to result in a series of explosions as beloved of dramatic films.

 

Garage door bottom seals are very approximate so petrol would get through, or you can leave a gap at an edge.