Suspended Floor with Foil

[lukewellington]

Hi,
Could you please tell me how to go about modelling a suspended timber floor with reflective foil attached to the underside of the floor joists. I am unsure what value to put for the insulation as there is nothing else other than the foil and I have read that the foil itself does not have an R-value.

Thanks

[Albrecht Stoecklein]

Hi Luke,

You could enter it as shown below:



However, Clause H1 allows you to assume that any suspended and sheltered floor with foil has an R-value of at least R-1.3.

Clause H1 Replacement Table 1:
(4) Carpets or floor coverings are not included in the floor R-value. The floor R-value is met by concrete slab-on-ground
and suspended floors with continuous closed perimeter with 100 mm draped foil. Exposed floors will require
additional treatment (e.g. pole houses).

Hope that helps.

Sunny regards

Albrecht

[kanim686]

Thanks for your kind info

[eion.scott]

Hi Albrecht, do you know if sisalation foil can be recycled? Suspect most is dumped, so wondering why it's removed at all during bulk insulation retrofit. Is there any issue with condensation if it's slit and folded up against the floor and held up by the new insulation? I'm thinking it's on the warm side of the thermal envelope, so not sure why moisture could be a problem?

[Albrecht Stoecklein]

Hi Eion,

Hmmm, not sure. I don't think it can be recycled. The aluminium content is probably so small that it does not make ecological and economical sense. Roman Jaques from BRANZ probably knows for sure.

I did a bit of research on the EECA website but did not come up with any clear answers why it needs to be removed. I do believe that it has something to do with moisture issues. You are correct that the foil is on the warm side of the bulk insulation. That means condensation should normally not be an issue.

The difference to the status quo is that there is no air gap between the foil and the underside of the floor. So that means that any moisture could not evaporate as easily, in particular if you have point sources of moisture (a dripping pipe, a spilled bucket of water, etc.)

Sorry, am not of a lot of help here

Cheers

Albrecht

[Kisame]

Is a formula that has principles