Mako

I have been offered supply and fit solution, regardless of the size. they also offer a SIPS panel option which they crane off and install on the same day, with concrete pour next day. it sound too good to be true but that would get around that issue. Otherwise i can see only benefits in full concrete structure insulated externally. what are your thoughts?

Hi Jack, thank you for your input, but I think we have crossed wires.. the point I was trying to make was, regardless of insulation used, you either have thermal mass provided by concrete or you don’t when building with timber. Concrete having the high density, heat storage capacity means that it will absorb heat easier that timber framed building. In terms of solar gains, I meant gains you get through windows not the walls. I also mentioned that the model would have same Uvalue, not worried about the thickness. And the temperature figures were from real project of similar size and orientation, where one was build in exposed concrete with concrete floors and the other in timber. Why does the Celulose 30’C drops, it’s because it’s hard to live in a house at that temperature, so you open windows to cool the house down, and the energy you gained for free has been let out. Concrete house doesn’t need to get rid of the free energy as it has the capacity to store it, and because of the density of concrete it can absorb more heat than the air in the house. When the heat is stored it will reflect it gradually back into the room. Concrete and the air in the house will be of the same temperature, if the air cools down, the walls will balance it, say walls are at 23’C and the air temp suddenly dropped to 19’C depending on the amount of air and thermal mass you might get closure to 21’C, where walls will heat the air in the house, in the process will loose the heat they stored. Does it make sense? sound proofing, have you been in a concrete house? With 50-60dB sound reduction between walls? Massive difference compared to TF. I’m glad that you would like to improve and build a concrete house, I have had a friend who was a contractor blowing cellulose into cavities Of walls even pitched roofs, but he said that only issue cellulose has that it self compacts after installation and that can create voids. im trying to find a reason why not to build using concrete with external insulation.

Ok, thank you, I will try answer your points: The information you mentioned is easily obtained from the type of concrete you are going to use? density conductivity heat capacity, just my thinking. The map you proposed, and the passive house software, using those indications and tools its the closest we can get to, to what we want to achieve at the design stage, but reality is different more often than not. that applies to many systems across the board, aiming for passive house standard. in terms of overheating, I should have said New Builds, we can’t really account for good old houses we built after WW2, they can’t really overheat as they don’t hold any heat, hence we need all this energy in the UK to heat all these homes. Sooner we realise that they need to be knocked down and rebuild the better. I can’t argue, about the thermal mass, as the evidence is coming from homes already built, but the poof is there. we just don’t want to see it, as we are still pushing TF agenda. as accurate as possible, but that’s an impossible task, I think.

Hmmm, render it’s not quite waterproof it’s classed as water repellent, if you render your basement walls it will leak, because render absorbs water, but because its applied vertically water will run off it. And it will dry quick after that.👍

Easily repaired yes, but it would involve rendering again as the patch work can’t be matched, as render will bleach in time. done it in the past, you will need to paint over with silicone paint at very least.

It might be all too late now, but there are systems for suspended floors where you can install UFH straight into the concrete and insulate from underneath, winwin solution

Who will calculate those on daily bases, as you can’t predict them?

Hmm, that’s the weak part of EPS or even XPS cladding, the compression strenght it’s not strong enough to withstand any impact. I have seen kids playing bow and arrow games at a council estate where they applied EWI System. the arrows where penetrating the render with ease. render is only cosmetic really.

Completely agree with you on that, there are many factors to consider, im not denying that. lts say a concrete building with external insulation delivering the same Uvalue as cellulose blown or TF structure. Same designs. The Concrete core would be able deal with solar gains and use the capacity of concrete core to absorb heat and store it, because of the thermal mass (density) of concrete, the means that room/house would increase the concrete temp from usual say 21’C to say 23’C which would mean the temperature in the house was 23’C. in cellulose/TF house the internal temperature would be say 30’C, you would struggle to stay in that house without opening windows and letting all the free energy out to heat the planet, rather than keep it inside, stored in the walls. At night temp. Drops and concrete walls starts releasing the heat back to the room. This process is not instigated it work by itself. In the cellulose/TM house temp would have also dropped, and it’s now relying on heat source to top it up. This is how I understand it, please correct me if I am wrong. and I have not mentioned the other benefits concrete provides, Airtightness, soundproofing, solid feel, as long as all the detail is done right.

I agree with you, but what SI units would you like to attach to it? how would you quantify Solar Gains? We know they happen because every other house has got issues with overheating, but how much it overheats depends on many factors, orientation, size of openings, quality of windows, etc, even passive house software struggles to deliver accurate calculations. It’s all a guess work. In the same way with thermal mass, we know it’s there we know it works, it just depends on design/orientation and size/quality of windows, but even than it’s hard to calculate it, because you can’t predict how much sun exposure one will have, same like with solar panels, nobody know how much they generate before hand, but we all know they work, and you can see after the performance what has been generated. Same like with concrete and thermal mass, you can see it on the energy usage per month/year and compare similar size building. It’s hard to measure and I believe them.

Thank you, that is close to what I have read elsewhere. appreciate your input

Ok, agree with you it’s perhaps harder to quantify, but it’s a proven thing, you only need to look at projects that has been build in concrete and insulated externally, they perform better, reduce energy required to heat, they don’t overheat, and offer balance temperature in the house, throughout the year. Energy costs are rising, I’m only trying to build something that will cost me less to run in the future.

Thank you Nick, I found the compressive strengths, would you know what loadings of the fixings can the reinforced EPS take?

You could say that when it’s in its original form, in the ground, after the processes by mr Knauf that changes massively, I seen that on previous posts and it has been contradicted, when processed to gypsum plaster or plasterboard. All you need to do is to weigh 1m3 of Gypsum plaster or plasterboard, and you won’t get 2700kg

Hi Ian, well what I have researched correct me if I’m wrong, thermal mass like you say can be any dense product, with ability to absorb and store heat. They say concrete is probably the closest to ideal material considered for thermal mass, due to density, it can accumulate, store and transfer heat. More concrete you have available (exposed face, not insulated) better it can deal with fluctuation of temperatures. Apparently it’s all about timing, when you trying to prevent building from overheating for example, if you have applied plasterboards on the walls, or insulation internally covering the concrete it will take a lot longer for the heat to transfer to the concrete core through the insulation, and also lo longer for the heat to react if the room gets colder (say at night). If the concrete was exposed it would react much faster. In theory Internally insulated walls would not prevent from overheating similar to TM structures. Thats my understanding of thermal mass Brick outside of the Insulated envelope could be classed as thermal mass, but no good to you, as it doesn’t help to stabilise your temperature internally. If it was inside of the thermal envelope it could be classed as thermal mass. but because bricks and lightweight blocks have low density compared to concrete their heat capacity would be much lower, compared to concrete. In layman’s term I would not be able to absorb great deal of heat when required. That’s what I understood when researching about Thermal mass