Building a workshop in an old stone built barn

[Jonm]

Remind me what the proposed heating regime is meant to be, a quick scroll through isn't giving me the reference. Think I saw woodstove mentioned briefly? Maybe I should've said heating regime and occupancy pattern. These provide the context for the insulation requirement.

Spot on, David66 needs to tell us what temperature he wants and how long for during the winter months. Also what the average external temperatures are and does he want the heating to be effective when it is bitterly cold, say -5degC outside. It can be very cold in Scotland. Also heating method and size of this box he is building.

 

[rogxwhit]

That'll be intermittent heat then. Which is bad news for tools and rust, because every time the air cools there'll be condensation on steel surfaces.

Sounds as if a modest amount of insulation would suit, though. What might the periods of occupancy be, and what type of activity is likely?

 

[David66]

Spot on, David66 needs to tell us what temperature he wants and how long for during the winter months. Also what the average external temperatures are and does he want the heating to be effective when it is bitterly cold, say -5degC outside. It can be very cold in Scotland. Also heating method and size of this box he is building.

Happy to wear a jumper, so mid teens centigrade. Would need heating to get there from October to March say. Average temps are between 8C and 6C during this period. If it's less than -5C - I'll probably not bother! Box will be around 3.6m by 5m, by 2.5m high.

 

[Jonm]

Happy to wear a jumper, so mid teens centigrade. Would need heating to get there from October to March say. Average temps are between 8C and 6C during this period. If it's less than -5C - I'll probably not bother! Box will be around 3.6m by 5m, by 2.5m high.

Ok, I will try and do a calculation later, unless someone else jumps in and does it. Need to get on with some jobs around the house.

 

[rogxwhit]

As a baseline, how about 50mm insulation in walls & ceilings ... forget the floor.

I think you need to concentrate on structure (especially that of the floor), and following that it seems that walls & roof only need a single skin internally with the insulation outboard of that.

Unfortunately for any form of glazing there's an added insulation / cost equation. :-(

 

[Jonm]

I will try and do a calculation later

Had a quick look at this, used the celotex online calculator for u values. It is a bit limited, not allow zero insulation thickness Etc. U values are W/m2K

Floor, insulation between joists, only allows for 400 joist spacing, standard floor board thickness
20 celotex 0.55
50 celotex 0.37
75 celotex 0.29
100 celotex 0.24

Ceiling, insulation between joists, 600 rafter spacing, 12.5mm plasterboard thickness
20 celotex 0.89
50 celotex 0.46
75 celotex 0.34
100 celotex 0.27

Could use ceiling values for wall. Not sure why it is giving such a big difference for the 20 mm celotex in floor and ceiling.

This is a start, I will send some calcs later to give heating requirements.

 

[rogxwhit]

Not sure why it is giving such a big difference for the 20 mm celotex in floor and ceiling.

I assume that it factors in location and that in a given space there'll be convection currents. The temperature will tend to be higher at the ceiling than at the floor, so there'll be a steeper temperature gradient through the envelope, thus faster heat loss? That's just my primitive take on it & I'm open to correction.

 

[rogxwhit]

It would be good if natural light could be 'imported' - apart from the qualities it can have as a work light, it also has psychological benefits ...

 

[David66]

Had a quick look at this, used the celotex online calculator for u values. It is a bit limited, not allow zero insulation thickness Etc. U values are W/m2K

Floor, insulation between joists, only allows for 400 joist spacing, standard floor board thickness
20 celotex 0.55
50 celotex 0.37
75 celotex 0.29
100 celotex 0.24

Ceiling, insulation between joists, 600 rafter spacing, 12.5mm plasterboard thickness
20 celotex 0.89
50 celotex 0.46
75 celotex 0.34
100 celotex 0.27

Could use ceiling values for wall. Not sure why it is giving such a big difference for the 20 mm celotex in floor and ceiling.

This is a start, I will send some calcs later to give heating requirements.

Thanks Jon - really appreciate the thought going into this.

It would be good if natural light could be 'imported' - apart from the qualities it can have as a work light, it also has psychological benefits ...

There are 2 large translucent panels in the roof, which let in a bunch of light. I plan to insert similar panels into the inner roof so that the light comes through.

 

[Jones]

The floor/ceiling values are different as heat rises. Insulation will only keep heat in if you actually add heat ,if you are reluctant to pay for that then a bit of insulation won't make much difference to the temperature inside. Regarding insulating the floor expanded polystyrene will be cheaper and for an occasional and temporary workshop should be adequate.

 

[Jonm]

Thanks Jon - really appreciate the thought going into this.

There are 2 large translucent panels in the roof, which let in a bunch of light. I plan to insert similar panels into the inner roof so that the light comes through.

Here are some calcs, they are more for sizing a radiator than working out cost of heating. For example I have assumed outside temperature of 0C wheras it will generally be 6C. Air changes is another area.. Another point is heat required to get the workshop and it’s contents up to temperature,

I cannot post the excel spreadsheet but can send it to you if you wish. If there are any mistakes in it someone on here will spot it. Calcs are for 50mm celotex.

 

[Jonm]

I assume that it factors in location and that in a given space there'll be convection currents. The temperature will tend to be higher at the ceiling than at the floor, so there'll be a steeper temperature gradient through the envelope, thus faster heat loss? That's just my primitive take on it & I'm open to correction.

The floor calc assumes timber floors wheras the ceiling assumes plasterboard so that is one difference. As you say there is a temperature gradient in the room and generally the temperature is higher near the ceiling so maybe the calcs are taking this in to account.

My concern was that generally the ceiling values are about 25% more than the floor but for the 20mm insulation they are 60% more. I went back and checked the results as I thought I had made a mistake, on the basis if something looks wrong it probably is.

 

[David66]

Thanks guys - appreciate this.

I'm still looking at cheaper alternatives to PIR boards. Came across thermal fleece and rock wool. For floors you install it on top of plastic netting, on which it sits. That would work for the ceiling too - but how would you attach it to the stud work on the walls, so that it doesn't just collapse before/after you put on the OSB sheeting?

 

[Adam W.]

So what's the issue here?
Presumably there's plenty of stone to be found under the soil.
Could have another shed with the leftovers.
My shed is a bit drier from doing the same kinda thing.
View attachment 141871
I don't know anything whatsoever about building, but seems to me a timber shed in a wet stone shed would rot, and besides who wants a suspended floor compared to concrete or whatever.

Can this building be raised whilst you're at it, getting the floor higher than the ground
That would presumably be easier to put a level floor and membrane in and simplify other stuff like doors ect.

Having had a brief look at building an insulated shed from stone,
it seems this is not a done thing.
I guess you folks in the UK do it though, as you folks have older buildings than we do.

Best info I've came across would be stone cladding,
as I've thought about using stone I have for a wee potting/garden shed.
I was toying with the idea of making a block wall inside,
and stone course on the outside (not cladding/stone on edge)

Sorry if I'm derailing the topic, just figured posting this if it may be a consideration?

A bit late to the party, but as stated a loooooong way above, it's not his shed.

 

[Jonm]

Thanks guys - appreciate this.

I'm still looking at cheaper alternatives to PIR boards. Came across thermal fleece and rock wool. For floors you install it on top of plastic netting, on which it sits. That would work for the ceiling too - but how would you attach it to the stud work on the walls, so that it doesn't just collapse before/after you put on the OSB sheeting?

David, if you have not done so already I think it would help if you priced this up without any insulation, then decide what money you have to spend on insulation. You have, floor joists, floorboards, stud walls, wall surfacing, two doors, two door linings, locks, handles, hinges, roof lights, wood burning stove, flue, flashing kit through the roof, electrics, damp proof membrane etc. then add 15% for the ancillary bits like screws, foam etc.

You may find that it is too expensive without any insulation and have to rethink the project.

As for rock wool in the walls, netting on the back to stop it falling out against the damp stone walls, should then stay in place to fit the osb. For the ceiling is there sufficient headroom to fit ceiling boards and put rock wool on top as you go, then do last bit from the main area of the barn. Pushing Rockwool up between joists from underneath then trying to keep it in place would be a horrible job, I would avoid it.

 

[David66]

David, if you have not done so already I think it would help if you priced this up without any insulation, then decide what money you have to spend on insulation. You have, floor joists, floorboards, stud walls, wall surfacing, two doors, two door linings, locks, handles, hinges, roof lights, wood burning stove, flue, flashing kit through the roof, electrics, damp proof membrane etc. then add 15% for the ancillary bits like screws, foam etc.

You may find that it is too expensive without any insulation and have to rethink the project.

As for rock wool in the walls, netting on the back to stop it falling out against the damp stone walls, should then stay in place to fit the osb. For the ceiling is there sufficient headroom to fit ceiling boards and put rock wool on top as you go, then do last bit from the main area of the barn. Pushing Rockwool up between joists from underneath then trying to keep it in place would be a horrible job, I would avoid it.

Words of wisdom.

I've done a rough estimate, but I need to go back to the shed to to finalise measurements as my thinking has developed. Should be able to do this in the coming week/weekend.

I'll report back!

P.S. Yes, there should be enough room to do as you suggest in the ceiling.

 

[Jameshow]

You can get off cuts of kingspan off eBay.

Polystyrene would be my default choice, I'd avoid rockwool at all costs from an ichy point of view.

Sheep's wool would be better tbh.

 

[mikej460]

With insulation there is the law of diminishing returns to consider, bear in mind that you don't want to live in this space but just comfortable to work in and reduce rust issues. I would use 60 to 100mm polystyrene in the floor (check eBay POLYSTYRENE EPS 70 INSULATION SHEETS 100MM 2400 X 1200 MULTI list 6 for £185 | eBay where I bought mine, great product and service), Knauf Earthwool in the walls and in the roof (but you need to fit 9mm OSB3 to the inside of the roof joists to stop you wearing it.

 

[Jonm]

I'd avoid rockwool at all costs from an ichy point of view

Very true, I would use it between/over ceiling rafters when installed from the attic above, elsewhere I would avoid it. Hate installing the stuff.

 

[Jones]

For between roof joists to there are special mineral wool rolls which spring in and won't fall back out immediately , itching isn't really a problem with the decent modern stuff. Rockwool rafterline is one I've used several times and it can also be used vertically, getting hold of less than a pallet can be difficult and expensive though.