U-Values

Slates

I'll be using PIR insulation to give the following U-values on a standard block house
Ground floor 0.21 W/m²K
Cavity wall 0.22W/m²K
Warm Roof 0.18 W/m²K
Cold Roof 0.14 W/m²K

Do you think I should bring these down further ?

sydthebeat

How have you calculated then slates??? did you use the SEI calculator?

what construction are you planning??

sinnerboy

those are good values

Step 1

in context ...........

DRAFT TGD 2007 Part L requires ( actual TGD 2008 expected any time soon )

walls 0.27
floors 0.25
roofs 0.22

SEI Passive house guide

walls 0.175
floors 0.15
roofs 0.15
with an almost total elimination of cold bridging ( very important when you insulate very highly )

Insulation is the easiest measure to demonstrate a cost benefit gain

Next sort windows ( TGD 2.2 SEI PH 0.8 )

Step 2

Ventilation / air tightness

Consider HRV . ( Heat recovery ventilation whole house system (

Factor in an air tightness test
( TGD n50<10 SEI PH n50<.6)

Step 3

boiler inefficiency + heating controls

Step 0 ( first thing to do )

Get a preliminary BER cert . Take advice from an assessor .
Get a good architect or architectural technician to implement the strategy after that

Slates

sydthebeat wrote: »

How have you calculated then slates??? did you use the SEI calculator?

what construction are you planning??

Standard Irish.......

Flood
150mm slad
60mm PIR with 20mm upstand
Radon
Sand
Hardcore

Walls
Render
100mm Dense block
40mm cavity
75mm PIR
100mm Dense block
Render

Warm Roof
Slates
50x25 battens
50x25 Cbattens
Breather membrane
Trusses @ 600cc
100mm Pir
38x12.5mm pir/plasterboard laminate
Skim coat

sinnerboy

Slates wrote: »

Standard Irish.......

Flood
150mm slad
60mm PIR with 20mm upstand
Radon
Sand
Hardcore

Walls
Render
100mm Dense block
40mm cavity
75mm PIR
100mm Dense block
Render

Warm Roof
Slates
50x25 battens
50x25 Cbattens
Breather membrane
Trusses @ 600cc
100mm Pir
38x12.5mm pir/plasterboard laminate
Skim coat

I get u values ( assuming lamda for ins of 0.023 ( kingspan )

floor 0.38 - need to double insulation to floor to get 0.2

wall 0.26

roof 0.18

sydthebeat

just remember with these new revised u values that they are NOT target u values...
they are minimum u values allowed when the dwelling complies with 40% efficiency compared to the MPCDER...

In practise if your dwelling has these u values its very likely that it wont comply with Part L as it wont be 40% more efficient.
In practise the current u values or better will have to be achieved.....

ardara1

sinnerboy wrote: »

I get u values ( assuming lamda for ins of 0.023 ( kingspan )

floor 0.38 - need to double insulation to floor to get 0.2

wall 0.26

roof 0.18

Can't calculate the floor u-value without the floor area and exposed perimeter - can u post them for me.

roof - 100mm unbroken might get a good value but I'm assuming you're putting it BETWEEN rafters? - this won't meet regs - about 0.35 at a guess -

Give me the make-pu and I'll calculate them for you.

Just ran 5 house type thru the new part L - NO wall below 0.22 passed

The smaller the property is the more difficult to pass.

Slates

The U-values were given to me by the insulation provider................:eek:

Slates

Please see bellow calc's


Construction typeElement: Solid Ground floor - Ground Floor InsulationSolid ground floorInternal surface emissivity: HighExternal surface emissivity: HighConstructionBridge DetailsThickness ThermalThermalPitchConductivity Resistance (º)(mm)(W/mK)(m²K/W)--0.040Inside surface60.01.4010.043Screed - cast (BS5250)60.00.0222.727Quinn Therm QF---Polythene,1000 gauge (0.25mm) (BS5250)--0.170GroundGround Floor DetailsCalculation method : EN ISO 13370 Perimeter: 48.60mArea: 121.00m²P/A: 0.402m Floor type: Solid floorEdge insulation: VerticalInternal surface resistance : 0.140m²K/W External surface resistance : 0.040m²K/WInsulation thickness: 25.0mmInsulation conductivity: 0.022W/mKInsulation depth: 150mmU-value - 0.21W/m²KU-value, Combined Method : 0.21 W/m²K (upper/lower limit 2.980 / 2.980 m²K/W, dUf 0.0000, dUg 0.0000, dUp0.0000, dUr0.0000, dUrc0.0000)(Correction for mechanical fasteners, Delta Uf = 0.000W/m²K)(Correction for air gaps, Delta Ug = 0.000W/m²K)

Mellor

ardara1 wrote: »

Can't calculate the floor u-value without the floor area and exposed perimeter - can u post them for me.

roof - 100mm unbroken might get a good value but I'm assuming you're putting it BETWEEN rafters? - this won't meet regs - about 0.35 at a guess -

Give me the make-pu and I'll calculate them for you.

Just ran 5 house type thru the new part L - NO wall below 0.22 passed

The smaller the property is the more difficult to pass.

Thats one of the biggest downfalls to the BER system. As its based on a per m2 value. Smaller buildings suffer.
It makes perfect sense that reducing, or keeping the area low will improve total energy used. But the per m2 value is higher due to constant energy users, ones not related to floor area. There may be other reason for the falloff also.

Slates wrote: »

The U-values were given to me by the insulation provider................:eek:

The provider most likely provided a floor u-value based on average P/A ratio. But ardara is spot on, the actually floor value can't be calculated.


I edited the post above to highlight perimeter, area and P/A ratio

ardara1

Hi Slates -

Results were difficult to read.
Theres a floor and a bit of pitched roof mixed up here -
I noticed the calcs used a lambda of 0.022 for PUR - I think all boards are 0.023 - I got these results

Wall - 0.23
Floor - 0.22
Sloped roof - 0.25

Roof will definately need to be improved - I'd aim for
Walls 0.20 Floor 0.18 - roof 0.11 (difficult on slope) - with these I'm able to get most designes to the new 40% improvement asked for in the new Part L

Same values will work to get an A rated - BUT the detailing is CRITICAL - would need to use details that will achieve a Y-value of 0.04 (Basically drylining everywhere!)

Mellor

Would insulation on the outside of the rafers improve the detail by much. ie no cold bridges. Even say, 50/50 between and on top,.
Do you think is viable to dry-line past the floor. To dryline, then install floor, breaking the drylining only at the wedges. I've been thinking over these details recently. Going to start a tread on details later today I think.

ardara1

Putting the full 100mm OVER the rafter would achieve 0.20 (Current regs) you'd need to be careful about wind upload and shear - the proper fixings should be specified (Helifix in Eng will do the calcs for you before supplying fixings)
I was at a passive house in Germany recently where the put 160mm over and filled the 150mm rafter (The designer preferred it to be ALL over) - they called it a 'Thin' roof!!!!!

Mellor

What support did the Germans have over the insulation. I imagine that has some sort of OSB before the battons. Seams to be common over there. I imagien it would greatly help support re uplift.

sinnerboy

My experience with roofers is they hate insulation over rafters - they "can't" find the structure to nail their tiling battens on to ......

Same with copper / lead roofs - make the insulation layer "too" deep over the structural timbers and prepare to hear some onions peeling .....

sas

Not to ask a stupid question, but surely the weight of the tils\slates would compress any insulation not specifically designed for this purpose?

I just get the impression that the discussion is here literally about sticking sheets of kingspan on top of the rafters. Or am I jumping to conclusions.

This is particularly relevant to me so I would really like to get more details on this.

ardara1

sinnerboy wrote: »

My experience with roofers is they hate insulation over rafters - they "can't" find the structure to nail their tiling battens on to ......

Same with copper / lead roofs - make the insulation layer "too" deep over the structural timbers and prepare to hear some onions peeling .....

So true - it's difficult on site - so lets botch it!

looking at the new part l - all roofs at 0.11 - things are going to have to change. How do you hit this with a 150mm rafter? - 125mm PUR between the rafters (allowing 25mm spave to allow membrane to sag) AND 100mm BELOW! They'll have the same problems hitting the rafters form the underside - and the residents will have to be vertically challenged

Slates

ardara1 wrote: »

So true - it's difficult on site - so lets botch it!

looking at the new part l - all roofs at 0.11 - things are going to have to change. How do you hit this with a 150mm rafter? - 125mm PUR between the rafters (allowing 25mm spave to allow membrane to sag) AND 100mm BELOW! They'll have the same problems hitting the rafters form the underside - and the residents will have to be vertically challenged

What are the new part l u-values?

Please see you pm

Mellor

sas wrote: »

Not to ask a stupid question, but surely the weight of the tils\slates would compress any insulation not specifically designed for this purpose?

I just get the impression that the discussion is here literally about sticking sheets of kingspan on top of the rafters. Or am I jumping to conclusions.

This is particularly relevant to me so I would really like to get more details on this.

Rigid insulation is not easily compressed, the weight of the tiles is nowhere near the weight of a screed or full slab.

sinnerboy

ardara1 wrote: »

looking at the new part l - all roofs at 0.11 -

..... know more then the rest of us A1 ?

just checked DOE site - no revised TGD yet

rejkin

does anyone know a website where you can get updated u-values?

sydthebeat

rejkin wrote: »

does anyone know a website where you can get updated u-values?

Updated from what??

if you are talking about the new Part l building regs (due to start for any dwelling applied for permission after 1st july 2008) then check the relevant thread....

otherwise you need to give a bit more information....

rejkin

yeah sorry,checked it and got the information,just needed accurate u-values for a college project

sinnerboy

u values are just part of a mix to achieve energy efficiency and limit co2 emmisions

a good start point is this exercise on DOE website

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,15662,en.pdf

9 different house types and measures ( including u values ) to achieve compliance with
2005 regs ( 1 st 2 pages )
current regs ( 2nd 2 pages )

Very important also
air tightness
ventilation method
detailing to eliminate cold bridging
selection of heat source ( current regs require min amount renewable )
user behaviour - current regs require end user information

mahoney.john

Slates wrote: »

I'll be using PIR insulation to give the following U-values on a standard block house
Ground floor 0.21 W/m²K
Cavity wall 0.22W/m²K
Warm Roof 0.18 W/m²K
Cold Roof 0.14 W/m²K

Do you think I should bring these down further ?

The following are some typical U-values of building components. (This may widely differ depending on the
composition of each item, variations in conditions, variations in physical properties etc.)U Value of Glass = 5.68 W/m2degC (single glazing)U Value of a wall = 1.76 W/m2degC (Brick & Plaster)U Value of a Roof = 0.971
W/m2degC (insulated concrete Roof Slab)

It is apparent therefore a lower value in your building envelope saves you quite a lot in energy bills.