Heating system for small outbuilding

[markocosic]

Video calls  you want diffuse light coming from in front of you and a quiet room. North facing window. Desk with you looking at screen and out of window. Light comes from behind screen onto your face. Or desk facing white wall and a desk lamp (or two) face away from you,  bouncing off the wall, and hitting your face.

 

 

Windows? They go in walls. Same problems as downlights for an office. Noisy in the rain too for calls. Difficult to seal around. Difficult to fit blinds to. Get covered in bird poo. No windowsills for plants and other ticky tacky.

 

 

Roof? Make sure it still has a fall after all the wobbliness of the roof. Make sure that your drainage detail can't go wrong (e.g. all water falls ff the side into an external gutter rather than any internal drainage) Then pick a covering that's adequately waterproof and will remain so after UV, extremes of temperatures, birds pecking at it, cats with sharp claws dancing on it, etc.

 

I don't have any experience using EPDM for a whole roof. That stuff is attractive for being one piece but 1.5 mm doesn't sound like a lot. Ask a pro flat roofer what they'd use on their own home. Probably 3-layer felt applied properly if they have all the tools. It's laborious but will last >30 years.

 

 

Porch? Entry door overhang for rain?

 

[MP1]

Thanks @markocosic

[MP1]

On 16/04/2021 at 13:40, Nickfromwales said:

@MP1

You simply bond the PIR ( you could just use 200mm of much cheaper EPS if you have the depth? Not much in it performance wise tbh ) to the slab with foam, weight them down whilst curing, and then you don't need joists. The 2 layers ( lay in opposite directions per layer with staggered joints eg not just overlaid ) will give you a rock solid floor with zero bounce, and zero cold bridging through the joists.

Winner winner, chicken dinner.

You need to shutter the slab in a timber shoebox so you can get the slab flat and level so there are no undulations to transfer through the uppers layers, ( that's where attention to detail is very important, but you're laying a foundation anyway so no extra expense other than time / eye for detail ) and you're good to go. For DPM, just put a sacrificial 25mm layer of EPS on the slab, then put your DPM atop that ( will prevent any puncturing ) and then put whatever insulation you want atop that. so 175mm PIR and 25mm EPS would be the 200mm sandwich. 200mm should be doable as that will allow a bit of a rain splash zone at the bottom of the external walls. If you can get 150mm or 200mm of insulation in, that would be the best outcome, but if the floor is not heated, then you could probably get away with 25mm EPS and 120mm PIR as that will still be quite a high spec for what it is. 

 

@Nickfromwales I am sorry to bother you again. I am doing the floor now and I am not sure how to bound all the layers together.

 

I understand that I can use foam to bound the sacrificial EPS to the slab but what do I use to bound the DPM to the EPS and then PIR to the DPM? foam as well? 

Please could you help me understand how to do that?