energy efficient homes

[buildit1]

Hi.

I am going to be building my own property next year and have plans to start my own new build construction company after my own build has been completed.
The main requirement that I need is for the property to be as energy efficient as possible.
Regulations are changing frequently and as energy costs rise, this is going to be an ongoing issue with insulation sizes.

The first concern is insulation. A friend has recently built a property for himself and he has more than doubled the insulation requirements that was needed. Roughly 75% of a properties heat loss is through the floor, walls and roof and this is his reasoning for overcompensating in these areas. The extra cost from this alone will be recovered in 3/5 years compared to today's homes.
However he has also gone further by installing a GSHP, solar panels, fibreglass windows and an electric heat pump among other things.

He has been researching spray foam insulation and has found that it is superior to rigid insulation as it has similar thermal properties, but it can be sprayed into areas you could not normally reach. It also creates a much better air seal.

What I would first like to know is peoples experience with spray insulation, good or bad. Also if there are any other ideas of creating a more efficient home.

Many thanks.

 

[Inky Pete]

Roughly 75% of a properties heat loss is through the floor, walls and roof

Where does that leave for the other 25% to be lost through?????

Does heat disappear into some sort of wormhole in spacetime in order to leave the property without passing through either the floor, the walls, or the roof?

 

[buildit1]

Windows and doors.

Unless you like it dark and never go out.

 

[jeds]

I wouldn't have thought using spray foam insulation in a traditional build would have a significant effect on thermal value. If you really want good thermal value why not think about structurally insulated panels.

 

[buildit1]

Hi jeds.

This is the reason why I posted on here. I wanted to get some feedback from other people on ideas/experiences that they have.
I will definitely look into SIP panels.
The plan was to construct it out of timber frame with either 150/200mm external walls and instead of part filling with wool or rigid insulation, completely fill it with foam.
There are a lot of theories that sound logical when reading about spray foam, one of them being that you could never seal as much with rigid as you can with a spray foam.

The technical data on cost savings are also encouraging. It can save as much as 60/70% on heating costs and that is a massive plus on todays energy costs and future cost rises.

An architect that I use have said that if you were to construct a timber frame home and mass fill the property, including all ext and int walls, floor, ceilings and roof, then that property would be more efficient than homes built in 25 years time and as much as 50.

 

[^woody^]

It is not correct to think of spray foam as some magical panacea purely on the notion that it could be sprayed into every nook and cranny

Equivalent insulation values can be achieved with many other insulation types or other design methods

The design has to considered as a whole, which includes considering heating method, thermal mass, solar gain and passive ventilation.

There is more potential for spray foam to go wrong, or cause other issues than with other insulation methods

 

[Inky Pete]

Windows and doors.

Unless you like it dark and never go out.

Are your windows and doors not in the walls then?

A window is simply a transparent section of wall, a door is simply a section of wall which can be opened.

 

[mointainwalker]

Roughly 75% of a properties heat loss is through the floor, walls and roof and this is his reasoning for overcompensating in these areas. The extra cost from this alone will be recovered in 3/5 years compared to today's homes.

As it stands, I just don't believe the above, except that it sounds like something someone may have said down the pub.

Would you/your friend like to repeat the u-values/degrees K calculations and cost of insulation that you have used to reach such a conclusion ?

This is especially appropriate to ceilings where I believe the existing 270 mm insulation goes beyond sensible cost/effectiveness and you are now saying 540 mm ?

Maybe your friend has some idea of what he is doing, but from the way you write, you seem to believe that twice as thick, is twice as good hence only half as much energy.

 

[big-all]

doubling the insulation will provide very very little return say the losses are 25%
lets assume the heat loss is 10kw for the whole house you reduce the heat loss by say 90% so you now have only 1kw loss you now double the insulation and again gain 90% reduction you only save 1/10th the amount off the first lot and at about say 25% off the total is only 25% off the savings at about 2kw
if we assume its 10p per kw the first level off insulation is saving 18p an hour and around 1.8p an hour for the second lot

so if your payback is around 5 years for the first lot off insulation the second lot will be 10 times longer at 50 years

now these figures are just very very rough estimates but just trying to show that doubling the insulation makes little difference rather than doubling the savings

 

[AronSearle]

He has been researching spray foam insulation and has found that it is superior to rigid insulation as it has similar thermal properties, but it can be sprayed into areas you could not normally reach. It also creates a much better air seal.

Spray foam is exactly the same as rigid foam. The difference is that rigid foam panels are often poorly fitted between studs, leaving gaps. If you install rigid foam properly, there is no difference. Either install the insulation as you install the studs (so you can push the stud's tight up against the insulation), or use spray foam just to fill the gaps.

As to general air-tightness, this is really a workmanship issue. You will still need to install a vapour barrier with spray foam (so I really don't see the point of it if you just install the rigid properly), and this really provides the air tightness, it must be properly lapped and sealed with DPC's etc.

And to bash home the point, I really really hate a lot of British builders, so many times I see them install rigid foam in the most appalling manor, with large unfilled 5-10mm gaps, make sure they fill those gaps with expanding foam.

SIPS' panels or cross laminated panels are the best thermally if you need to keep the wall thickness to a minimum (they are also better as it means more off-site construction). staggered joists, or I joists will be second best, and possibly about 5-10% cheaper.

Cross laminated timber panels are probably better than sips, structurally they are "much" stronger, they will also be much more durable against any unintended moisture exposure (I have tested some cross lam panels submerged in water, they mostly use a WBP bond whereas sips use OSB which does not like water). Some 7-9 story timber frames have been constructed with cross lam timber panels in London, just to give you an idea of their strength. With a cross lam frame you will often put rigid foam on the outside of the frame, then a cavity, and then your cladding material (always have a cavity with timber frame).

Also the cross lam frame will provide "some" thermal mass. In regards to thermal mass it is better to provide this with the inner walls/ concrete floor slabs or wall coverings, and then massively insulate the outer walls. remember standard block is lightweight and has a thermal mass comparable to lightweight timber frame, so if you go for brick and block you will want some dense block work in the core of your building.


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[buildit1]

Inky Pete.

There are five areas that are used for calculating heat loss and they are the floor, walls, roof, windows and doors. Although doors and windows (including roof windows) are part of the main structure they have to be included in the calculations as well.
The reason for this is, that the more external doors and windows you have, the more insulation is required to compensate for those areas which are not insulated. It may not be that much, but due to the amount of velux windows I have in the roof, I had to increase the roof insulation by 25mm.

mountainwalker.

I haven't gone into much depth with all the costs/savings, but I know that my friend has and this is the reason that I need to find all the info I can on the subject of energy efficient home. The only thing that I have done is used an insulation calculator. I need to find out exactly how to use the U values, so that I can convert these into how much heat needs to be used for the difference in insulation thickness.
I don't believe that twice as thick is twice as good, but as I said above I need to know how the U values actually work and I would also like to know at what thickness does it just make now difference.
Where did I mention 540mm?

big-all

I understand the equation that you have posted and in that sense it is pretty pointless.
Do you have any idea on how to calculate costs/savings from the U value.
Let's say you put 60mm of rigid in a traditional construction and achieved a value of 0.25 and then put 200mm of rigid in a timber frame and achieved 0.15, what does this actually mean for energy consumption.

AronSearle

I agree. I have seen some pathetic attempts of insulation being fitted and have also seen BCO's not pick up on the fact that there are gaps everywhere.
The reason I decided timber frame over sips panels is due to construction costs. The team of tradesmen that I use + a few things I undertake myself allows me to build at a very cost effective price. Having an outside company come in will increase those costs.
The carpenters that I use can now build the main structure and the savings are at least 35% compared to the cheapest timber frame company in my area.
I will look into SIP panels and see what the costs are and if I can have them supplied only and have my carpenters install them.

Thanks.

 

[mointainwalker]

Where did I mention 540mm?

Well, since the recommended amount is 270 mm and you write as below, I think it;s an honest deduction, don't you ?

and he has more than doubled the insulation requirements that was needed

.

Bit of a surprise that you say you don't know how U-values work. Better start learning for your own house.

By the way you initially wrote your friend has a GSHP as well as

an electric heat pump

So what is the latter - ?

 

[leew2]

an electric heat pump

An A/C unit?

 

[buildit1]

mointainwalker.

The electric heat pump is something to do with the heating of the house.
I agree that I don't know much (but should) about U values, but all I have done is adhered to what the BCO has told me to do. I know what is needed, but what I would like to know is exactly how U values work in comparison to heating costs.
If there was 100mm of rigid insulation in an external wall with an outside temp of 0c what would the heating costs be per day to keep that home at a temp of 17c compared to 50mm. What is the difference by increasing it bit by bit.

I'm going to have to look into this in much more detail. I've just been reading about low cost heating homes and the first thing that is noticeable is the thickness of insulation.

Thanks.

 

[mointainwalker]

The electric heat pump is something to do with the heating of the house

Yes, but that is what the GSHP is.

Well, when you know about U values , then you can calculate easily how much more heat you lose per extra degree K ( K = difference between int and ext temp in oC ) and therefore what the costs of different levels of different types of insulation in any given circumstance.