Shed floor insulation (not workshop)

[Welsh Brian]

Your thoughts appreciated.....

Need to build a lean to shed that will just be used for storage and not worked in and will have no heating.. My thoughts are it would be better to have have concrete floor with a DPC and no insulation. I think that this would make the shed less likely to go below freezing as the floor will be at ground temp which under cover, should not fall below about 5 degrees. With insulation below the concrete, the sub ground temp will not transfer into the slab. Main aim is to help stop the shed going below zero.

 

[artie]

A heater with thermostat is about the only sure way.
Even then a power cut is possible.
How imperative is it that the temp stays above zero?

 

[RobinBHM]

Your thoughts appreciated.....

Need to build a lean to shed that will just be used for storage and not worked in and will have no heating.. My thoughts are it would be better to have have concrete floor with a DPC and no insulation. I think that this would make the shed less likely to go below freezing as the floor will be at ground temp which under cover, should not fall below about 5 degrees. With insulation below the concrete, the sub ground temp will not transfer into the slab. Main aim is to help stop the shed going below zero.

I built a shed 5.4m x 2.7m

4x2 frame, 18mm OSB outside, tyvek housewrap, 25 mm battens, featheredge.

It's got timber joists and OSB floor

No insulation, I don't really get any condensation in it, it does get a bit below freezing, but not much.


Personally I think using quality breather membrane and 25mm air cavity is what stops it getting condensation.

I'm not sure about your ideas on the slab.

My thoughts are: if the shed is unheated, the concrete will be at the same temperature as the internal air temperature, which on a cloudy day and thus without solar gain will be same as external temperature.

I'm not sure you will gain much from insulating below the concrete as the slab perimeter won't be insulated and that is where the cold will creep in.

If the shed is having any glazing, you might be better spending the money on double glazing as that will reduce chance of condensation due to temperature changes during the day.

 

[Welsh Brian]

Totally agree with the use of breathable membranes and not allowing windows to be a source of condensation. Really looking for members thoughts on the temp of an concrete slabs as an anti freeze method. Yes the air temp on top of the concrete may drop but the temp below the slab will always be at least 5 degrees unless our climate changes so much that we start to get perma frost! heat will normally rise if I remember by schoolboy physics (ignoring the small radiate/convection(?) loss to the side)

 

[Wildman]

egg boxes/trays under the concrete makes for a warm floor.

 

[TheTiddles]

Insulation isn’t magic, it can’t make things hot or cold, it just slows the rate of change of temperature. The ground is at a relatively constant temperature if you go down a bit, but you do get frost on top of it. A shed’s internal temperature will mostly be determined by the air temperature outside it.

My garage has heated rooms above, insulated brick walls and has the heated house to one side with an insulated concrete floor, it was below freezing in there a couple of weeks ago.

What needs to stay above freezing that’s going in it?

Aidan

 

[Inspector]

If you dig down a couple feet and poor a concrete footing with a short wall to get above the surrounding soil you have two choices. Best option is to apply foam sheets to the outside of the wall and parge over the exposed foam to protect it and then pour the slab inside. Second option is to put the foam inside the foundation walls and pour the slab. That will keep the cold from getting to the slab but you might want to consider adding a solar collector on the shed roof to put heat into the slab when it is sunny if the contents have to be kept from freezing.

Pete