Thoughts On Insulation In A Siding Contruction

[necronx99]

Ok, the plan is a semi elevated bungalow with faux wood cement board cladding with an interior wall of wood paneling.

Suspended ceiling with bat insulation.

Thoughts and suggestions on optimal cavity space and options for in wall insulation types and effectiveness please.

[bbradsby]

Would love to help. First I need some info:

What is your proposed exterior wall construction - wood studs (please say no), metal studs, concrete frame with concrete masonry/brick infill?

Do you have a plan you could post for analysis, with an indication of North? North is up on the Chanote site diagram.

What are your overhangs' dimensions?

[bankruatsteve]

I'd go with the same bat insulation for the wall cavity that you have for the ceiling - shiny side out.

[Kwasaki]

Thoughts and suggestions on optimal cavity space and options for in wall insulation.

Sealed cavity space the bigger the better.

http://www.progressivefoam.com/

[bankruatsteve]

Thoughts and suggestions on optimal cavity space and options for in wall insulation.

Sealed cavity space the bigger the better.

http://www.progressivefoam.com/

Cavity with insulation bigger the better up to a point at which it's insignificant to be bigger. Air cavity over, I forget, a few inches is not better or worse - it's just the same for insulation value.

[bbradsby]

To the OP, what's your wall construction - blocks, studs...?

[Kwasaki]

Thoughts and suggestions on optimal cavity space and options for in wall insulation.

Sealed cavity space the bigger the better.

http://www.progressivefoam.com/

Cavity with insulation bigger the better up to a point at which it's insignificant to be bigger. Air cavity over, I forget, a few inches is not better or worse - it's just the same for insulation value.

A roof area is a big cavity so minimum 300mm thick insulation on a ceiling, more if you want.

Wall cavities standard widths 60mm - 100mm it comes down to what is practicle.

[Kwasaki]

To the OP, what's your wall construction - blocks, studs...?

He said faux wood cement board cladding with interior wood panels with which assume would have stud material between.

[bbradsby]

To the OP, what's your wall construction - blocks, studs...?

He said faux wood cement board cladding with interior wood panels with which assume would have stud material between.

...was my assumption as well, but as cement board cladding can be 'set' in a cement mortar bed over block/conc walls, and interior finishes of any kind can be installed in a number of ways, furring strips... I thought it best to make sure we have the whole picture of his exterior wall assembly.

[bbradsby]

Wood Stud Walls [god help you]:

-Shade the walls, first & foremost - with overhangs, trellises, even planting/trees... anything!

-100mm stud width; no structural info included here, just insulation considerations as requested.

-75mm-100mm batt insulation, foil faced one side, foil face installed on the exterior wall side;

-No air gap required - the insulation si one giant blanket of air gaps, none better.

Ceiling insulation [not roof surface insulation]:

-150mm of batt insulation.

-If you get foil faced, put the foil on top, facing attic.

General:

-stuff the insulation tight into all corners, no gaps!

-Im not a fan of the plastic bag insul blankets sold in LoS, as they don't allow water vapor to pass

unless gaps are left, and these will short-circuit your insul values.

-air infiltration is almost as big an issue as insulation with a full air volume change [of your

nice, expensive, cool inside air for hot outside air] occurring easily every half- to one hour if

you don't properly weatherstrip & seal all openings.

-use a light-colored, low mass roofing material so it reflects solar radiation and stores little.

White metal is best, for example. Plant trees that will get big fast on the West side of house.

-Shade & plant - don't pave - the sitework up-windstream of your house.

Edited February 19, 2012 by bbradsby

[necronx99]

Ok, yes it is a stud wall with cement board cladding and wood paneled interior.

Elevated house (1 meter) with a redwood floor. Wall thickness at this stage is 10cm..

Orientation of the house will be ~15 deg N/NE relative to the roof centreline.

Prospective plan is below. All rooms have ventilation to at least 3 sides with fairly generous roof overhangs and plan on substantial

shading from vegetation. Lots of vents to the ceiling, perhaps fan forced (solar).

Batts in the roof seems a given for insulation. For the walls anything fancy is probably out of scope, so as I see it it is either the same batts as the roof or

as someone posted in another thread, polystyrene sheets with a foil facing. Would the latter be the best giving both a radiant barrier to keep heat out and the

insulation barrier to keep aircon in?

plans

Example of finished look.

Edited February 19, 2012 by necronx99

[necronx99]

Several post have come down against wood studs, the reason?

Lot of red wood in the house, also anticipating a termite protection system.

Edited February 19, 2012 by necronx99

[harrry]

Hope you like feeding termites.

[bbradsby]

...Batts in the roof seems a given for insulation. For the walls anything fancy is probably out of scope, so as I see it it is either the same batts as the roof or

as someone posted in another thread, polystyrene sheets with a foil facing. Would the latter be the best giving both a radiant barrier to keep heat out and the

insulation barrier to keep aircon in?

Shading looks adequate. Think about fan palms or equal on East & West sides. They get huge and fan out like a Lanna hand fan, just two stories tall!

Foil-faced polystyrene provides best practical house insulation U- or R-value per given unit of thickness. Only Polyurethane is better, but insects eat it and it is most dangerous in a fire condition [You are using conduit & wiring device boxes, RIGHT?!], but super-insulating your house with its drafty wall construction, without adding an infiltration barrier, would be a waste of money. Insulate to around R-11 in walls, R-30 in ceilings & weatherstrip doors & windows really well if youre using AirCon that is.

[wpcoe]

General:

-stuff the insulation tight into all corners, no gaps!

How does that reconcile with leaving gaps around light fixtures? I thought a few gaps would not be all that critical if, say, 95% of the surface were covered with insulation?

[weedywhaoo]

Don't forget that a lot of heat will travel through your windows. Also note that a 2% moiste content

in the fiberglass insulation will decrease insulation with 50%.

[Kwasaki]

General:

-stuff the insulation tight into all corners, no gaps!

How does that reconcile with leaving gaps around light fixtures? I thought a few gaps would not be all that critical if, say, 95% of the surface were covered with insulation?

You don't have to leave gaps around light fixtures if you use the correct fittings.

[Kwasaki]

Don't forget that a lot of heat will travel through your windows. Also note that a 2% moiste content

in the fiberglass insulation will decrease insulation with 50%.

He could use thicker mirror effect glass or window tint film covering.

You can lose insulation values because of the wood stud but it can be beneficial to use a vapour barrier over the stud work before installing the fibre batt.

[wpcoe]

You don't have to leave gaps around light fixtures if you use the correct fittings.

What type of light fixtures would allow for insulation to butt up against them (on top of them?) i.e What feature is significant to look for when buying the light fixture?

[necronx99]

You don't have to leave gaps around light fixtures if you use the correct fittings.

What type of light fixtures would allow for insulation to butt up against them (on top of them?) i.e What feature is significant to look for when buying the light fixture?

Particularly with downlights there are two types. Cheap ones without and good ones with a heatshield that goes over the fixture.

I myself don't like them and will use hanging fixtures.

[necronx99]

Don't forget that a lot of heat will travel through your windows. Also note that a 2% moiste content

in the fiberglass insulation will decrease insulation with 50%.

He could use thicker mirror effect glass or window tint film covering.

You can lose insulation values because of the wood stud but it can be beneficial to use a vapour barrier over the stud work before installing the fibre batt.

Not you're sounding like crossy and naam. "Vapour barrier"? Plastic sheet?

[Kwasaki]

Don't forget that a lot of heat will travel through your windows. Also note that a 2% moiste content

in the fiberglass insulation will decrease insulation with 50%.

He could use thicker mirror effect glass or window tint film covering.

You can lose insulation values because of the wood stud but it can be beneficial to use a vapour barrier over the stud work before installing the fibre batt.

Not you're sounding like crossy and naam. "Vapour barrier"? Plastic sheet?

I'm flattered !! If your using foil backed firbreglass as " bankruatsteve " has said shinny side to underside of external cladding.

You already mentioned about polystyrene sheets with a foil facing.

If your just using plain fibre batts then for ( Vapour barrier ) there are cheap simple ways, materials like Polyethylene plastic sheeting or aluminum foil is good for using as a vapour barrier on the underside of the external cladding but tape any joints.

Another good and easy thing to do is just paint the timber stud work with a waterproofing sealer.

A spacer between the internal side of the wood stud and internal wood panels would help cut down any heat transfer.

Edited February 21, 2012 by Kwasaki