Hi,

I'm planning the, ongoing!, building of a passivhaus Vet Surgery in the Wigan area. Still struggling with deciding on a few details. Im planning on timber frame, warmcel insulation, probably on a passive slab. Nearly everything needs to be on one storey- I understand his dosent make for a very good form factor.

Any suggestions for making this build cost effective as its in an area of really low house prices?

The SE has advised that, as the site of a now demolished which had a cellar under part of it, there needs to be a uniform 1m of crushed, rolled material under the whole site. Does this sound excessive?

There maybe 100 visits a day so does the building need a draught lobby, should this be external to the thermal envelope or internal and insulated or not?

Theres a passive vets in Dublin, where the owner complains of overheating, would a 100mm slab be enough thermal mass or should I go for more?

Sorry, a lot of questions!

Thanks,

Chris

Posted By: bogal2I'm planning the, ongoing!, building of a passivhaus Vet Surgery in the Wigan area.

Sounds like an interesting project. I don't know what the passivhaus rules are for commercial buildings, and how they interact with what are presumably some specialist requirements. I'd suggest the first and very important step is to choose a certified passivhaus designer with experience of similar projects. I suspect you'll have particular ventilation requirements, both because of the number of people and also the presence of animals.

Im planning on timber frame, warmcel insulation, probably on a passive slab. Nearly everything needs to be on one storey- I understand his dosent make for a very good form factor.

That sounds like a sensible building method; the other I might consider is blockwork and EWI. The passive slab is a good choice, especially with dubious ground underneath. You're right about the form factor but that can be compensated by making the insulation a bit thicker - we have 400 mm of graphite EPS under our floor and 450 mm (IIRC) of Warmcel over our heads to compensate for the limited and fixed value available from our straw bale walls.

Any suggestions for making this build cost effective as its in an area of really low house prices?

Keep the design simple - maybe change cladding materials to make it more 'interesting' if necessary rather than putting kinks in the walls or roof, for example. Also make sure it is simple to build, using conventional solutions wherever possible. And make sure your designer and builders understand that you want to stick to your budget.

The SE has advised that, as the site of a now demolished which had a cellar under part of it, there needs to be a uniform 1m of crushed, rolled material under the whole site. Does this sound excessive?

I've got a 1.5 m hole under my house, because of clay and nearby trees. But 400 mm is filled with EPS and another 150 mm with the slab, so there's not 1.5 m of hardcore. It's not clear whether the SE will want 1 m of hardcore regardless or whether it might turn into 500 mm - you could ask Hilliard Tanner if your SE is dubious. But overall I'd say it sounds fairly reasonable; it's not an excessive depth and could have been much worse. Although does he mean the whole site including car park etc, in which case costs could mount up?

There maybe 100 visits a day so does the building need a draught lobby, should this be external to the thermal envelope or internal and insulated or not?

I think this is a question for your expert designer, perhaps with advice from the M&E engineer that designs the ventilation system. If you do need (or want) one, I'd think it was better external since it won't take expensive internal space, can be fairly simply constructed, and might improve the overall appearance if done carefully.

Theres a passive vets in Dublin, where the owner complains of overheating, would a 100mm slab be enough thermal mass or should I go for more?

There's also one in Schwanenstadt according to google. I'd certainly talk to as many owners of similar buildings as possible.

Google also tells me you are a passivhaus consultant (well done), so I expect PHPP will give you its estimate of overheating potential. Orientation and window positions are at least as important as thermal mass. Rooms with south or west facing windows will behave differently to others. If your M&E engineer chooses a heat pump, then you might have some cooling available if you need it.

edit: google also mentions Dogs Trust Loughborough

Posted By: bogal2Its mainly all those panting Labradors that send the summer temp up.

The 50 W dog, and lots of them! A heat pump definitely sounds attractive to me.

Oh, and the certifier is another useful source of advice if you use one.

I would seriously consider blockwork rather than timber frame, several reasones - sound and noise , slower temperature swings, then EWI, ventilation system in the loft should be easy and also easy to retrofit.

Sounds to me like no heating needed

I would recommend doing a thermal model to inform the design, a good one will tell you number of days with overheating, need to model in the dogs and equipment.