Suspended floor for a conservatory

[QuestionsQuestions]

Need some advice please.

We are having a conservatory built 3m deep, 5m wide (1 full height brick wall, brick piers and a small window on outside wall) The builder has built a raised floor as back door to ground is 600mm and has attached wooden joists to the top of the brickwork and filled these with polystyrene before puttting what looks like chipboard over the top...I am worried that this will not be insulated enough to keep the heat in when its cold...can anyone with any expereince of such floors please advise whether this polystyrene is enough... btw we are going to have underfloor heating and tiles over the top.

Any help greatly received

Thanks

 

[endecotp]

What thickness of polystyrene?

 

[QuestionsQuestions]

About 750 or 1000mm..also the floor has been built over just earth..will this effect the insulation?....or even maybe make it damp underneath the wooden joists?...
Thanks in advance

 

[endecotp]

A metre of insulation?!!!
How can you think that's not enough?

 

[QuestionsQuestions]

oops too many zeros 75 -100mm of polystyrene!!

 

[tomfe]

If that is the build up it's wrong for an extension but as it's a conservatory then anything goes.
As worrying about heat escaping from the floor you only have plastic sheets in the roof so most of the heat will be lost there.

 

[QuestionsQuestions]

Even though it is a conservatory it has two proper walls and we wanted it to be built like an extension as then it would have more chance of being a usable room for more of the year..as it is we are having argon filled glass throughout so i don't want any potential 'livability' be compromised because it has a floor that is not a thermally efficient as that of an extension...All i really want is to insulate as much as i can everywhere else...if it was an extension what would be the build up for an extension suspended floor? TIA

 

[tomfe]

You need to have a concrete over site below your suspended timber floor, you'll also need ventilation. Normally around 100 to 120 mm of pir. So for eps 150-170mm.
Without knowing the full construction of the build, you'll be getting a uvalue of around 0.4 to 0.6 at 75mm 0.3 to 0.5 with 100mm

How much insulation have you got in the walls? Have you got dg on your roof?

 

[QuestionsQuestions]

This is what I said to the builder today and he said he had checked with building regs and the floor was ok..and I am guessing this is because its described as a conservatory and as has been said anything goes..except for the fact that we want it as thermally efficient as possible...are the u values with the concrete oversite? do you know what they might be now..with the joists 600m above earth floor with air bricks and 100m of polystyrene?

Not sure what dg stands for...but we have double glazed, heat reflective glass sealed units, Argon filled with Pilkington “Activ” to the exterior pane and Pilkington “KS” to the inner, including “Self Clean” technology on the roof

 

[tomfe]

The concrete over site is to stop weeds growing it's required by building regulations but since you are not going down that route I would not worry.
You will have more insulation in the floor than a lot of other houses but with the level of glazing you have it will still leak a lot of heat regardless of what you put in the floor.

An extension would need a uvalue of 0.22 or less to comply with building regulations, if you give me your joist centers and sizes (width) I can do a more accurate u value calc.

Depending how long you plan to stay at your house you may find the law of diminishing returns will play a big factor.

 

[QuestionsQuestions]

Thanks. At a guess 39cm apart and 4.5cm wide (joists approx 3m x 15cm x 4.5) i will check in the morning..how do u calculate u values?

 

[tomfe]

Ok so 15m2 area 16m perimeter 100mm eps would give a u-value of around 0.34 so it's not that bad.
But really it's not worth worrying about.

 

[endecotp]

Ok so 15m2 area 16m perimeter 100mm eps would give a u-value of around 0.34 so it's not that bad.

You're including the side adjoining the house in the perimeter; I think it should only be the external (cold) perimeter. That won't make a huge difference though.
You could improve the insulation by lifting the chipboard and putting more or better insulation in place of what you have, but is it worth the trohble at this point?
I think you'll still be losing a lot more heat through the glazed roof.
Make it feel warmer underfoot by not putting down tiles. I like cork!

 

[tomfe]

You're including the side adjoining the house in the perimeter

I have no idea of layout so to make presumptions would be wrong here, better to take the worse case.

 

[QuestionsQuestions]

It is a lean to design..ad yes 5.2m across the back of the existing house..projecting 3m outwards...and we do not intend to move until someone carts us off to an old folks home!