Hiya, good video - I'm a civil engineer - if you're trying to keep something warm (or cold) ALWAYS insulate under the concrete slab - It's now mandatory for houses and even more important if you have underfloor heating where you have to add even more insulation above the slab. So the same logic applies to hot tubs.
Thanks for the comment Dave - really good to know! Where would you put the insulation for the slab, under the ballast or physically inside the slab with the rebar and just make it thicker so the strengh is not compromised?
@@Buildahottub lay and compact the sub-base (ballast) then lay a Damp Proof Membrane (DPM) then the insulation - 100mm minimum of PIR, then more DPM so that the insulation is encapsulated and cannot become wet. The concrete base can then be poured on top of that.
I work for a general contractor and I've never heard of dampproofing on both sides of the insulation for underslab insulation. Is that because you are using Polyiso insulation? We would typically use XPS insulation (which can get wet) under slabs with no damproofing on either side - Just 6 Mil or 10Mil Poly above the insulation . @@davidianwalsh
Thanks for the comment. Potentially yes, although the foam is quite soft so you have the potential for dents in your liner prety quickly that would not look great. Also, for hot tubs I dont recommend liners at all as it is very hard to find jet bodies that work with liners - as one of my case studies "Brandon" on www.buildahottub.com if you check it out explains. - hope that helps Andi
Hi Andy, I am wondering about the heat loss from the jets and plumbing? Is it possible to put all the plumbing in an 8" poured concrete wall and then insulate outside of that, so that the plumbing is also all insulated? Or is this a bad idea, since you can not access the plumbing in the event there is a leak?
Quite the question Jared - there are two schools of thought on this as you point out. Depends how confident you are on your plumbing - no reason it cant go inside of a wall - it is designed to do so. However, access is quite handy, especially if you spring a leak - what I dont suggest is doing 50/50 - I did on my own and it was a right pain when i needed to do some modifications! Thanks for the comment - Andi
Hi Andrew, a lot of that depends on the type of heating you have. I've found with my own block tub that the most economical way of running it is holding at 30C / 86F and then taking it up to 39C / 102F when i want to use it which for me is weekends only - with my air source, that takes about 90mins on average, a little longer if it is cold out. After use, i drop it down again. If you plan to use it daily, it might be worth putting in a system where you can schedule the heat (Control My Spa from Balaboa can do it) In that way, you could drop your temp down overnight to reduce running costs, if you were well insulated it would not loose too much, then heat it back up ready for use at the times you would be using it. All possible - depends on your heating method as I said (electric is slow for example) and the times you plan to use it - hope that helps! - Andi
@@Buildahottub huge help! Thanks for the thoughtful response. I plan on heavily insulting. I don't think the air source heat pump will be a good idea here in the Pacific Northwest since when I am going to want to use the tub the most will be in the winter.
Hiya, good video - I'm a civil engineer - if you're trying to keep something warm (or cold) ALWAYS insulate under the concrete slab - It's now mandatory for houses and even more important if you have underfloor heating where you have to add even more insulation above the slab. So the same logic applies to hot tubs.
Thanks for the comment Dave - really good to know! Where would you put the insulation for the slab, under the ballast or physically inside the slab with the rebar and just make it thicker so the strengh is not compromised?
@@Buildahottub lay and compact the sub-base (ballast) then lay a Damp Proof Membrane (DPM) then the insulation - 100mm minimum of PIR, then more DPM so that the insulation is encapsulated and cannot become wet. The concrete base can then be poured on top of that.
Our pools are always insulated under the slab even if there is a sub floor
I work for a general contractor and I've never heard of dampproofing on both sides of the insulation for underslab insulation. Is that because you are using Polyiso insulation? We would typically use XPS insulation (which can get wet) under slabs with no damproofing on either side - Just 6 Mil or 10Mil Poly above the insulation . @@davidianwalsh
Thanks for showing the different styles. Can foam be the inside layer with a liner over that?
Thanks for the comment. Potentially yes, although the foam is quite soft so you have the potential for dents in your liner prety quickly that would not look great. Also, for hot tubs I dont recommend liners at all as it is very hard to find jet bodies that work with liners - as one of my case studies "Brandon" on www.buildahottub.com if you check it out explains. - hope that helps
Andi
@@Buildahottub makes Sense, thanks 👍
Hi Andy, I am wondering about the heat loss from the jets and plumbing? Is it possible to put all the plumbing in an 8" poured concrete wall and then insulate outside of that, so that the plumbing is also all insulated? Or is this a bad idea, since you can not access the plumbing in the event there is a leak?
Quite the question Jared - there are two schools of thought on this as you point out. Depends how confident you are on your plumbing - no reason it cant go inside of a wall - it is designed to do so. However, access is quite handy, especially if you spring a leak - what I dont suggest is doing 50/50 - I did on my own and it was a right pain when i needed to do some modifications! Thanks for the comment - Andi
I live in a coldish climate. I want to use a block tub that will be insulated daily, what temperature would you recommend keeping the tub at?
Hi Andrew, a lot of that depends on the type of heating you have. I've found with my own block tub that the most economical way of running it is holding at 30C / 86F and then taking it up to 39C / 102F when i want to use it which for me is weekends only - with my air source, that takes about 90mins on average, a little longer if it is cold out. After use, i drop it down again. If you plan to use it daily, it might be worth putting in a system where you can schedule the heat (Control My Spa from Balaboa can do it) In that way, you could drop your temp down overnight to reduce running costs, if you were well insulated it would not loose too much, then heat it back up ready for use at the times you would be using it. All possible - depends on your heating method as I said (electric is slow for example) and the times you plan to use it - hope that helps! - Andi
@@Buildahottub huge help! Thanks for the thoughtful response. I plan on heavily insulting. I don't think the air source heat pump will be a good idea here in the Pacific Northwest since when I am going to want to use the tub the most will be in the winter.
Sit on a concrete bench in the winter for 10 minutes, then revisit the idea of insulating the slab 🥶