Topic: Environmentally friendly underfloor insulation

Environmentally friendly underfloor insulation 

Hello,

Do you have any recommendations as to the most environmentally friendly underfloor insulation product? I am looking to insulate my home (in Dunedin, NZ) and have found locating information about environmental impacts difficult to find.

Any information or advcie would be greatly appreciated.

Fiona

Re: Environmentally friendly underfloor insulation 

I guess that could depend a lot on your angle for environmental impact - energy used in manufacture, energy saved by installing, chemicals used/released, greenhouse gases, etc? Maybe a full lifecycle assessment?
That said, avoiding polystyrene might be high on the list because of the gases and chemicals used in production. But it's worth considering the effectiveness (R-value) of the different insulation products too - if you insulate with something that has a higher R-value then you'll be using less energy to heat your home, and therefore less GHG emissions over the installed lifetime.
And then there's the energy used to create the insulating material - bog standard foil insulation probably doesn't use much and gives OK insulation. The 'bubble wrap' foil (underfloor.co.nz) performs really well but would take more energy to make. Recycled wool insulation might be a good choice? (not sure about any glues used in it though).
Personally, I'd go for standard foil insulation - you're only losing around 10% of heat through the floor anyway, so why not save your money (and energy) for something else where you could have a greater impact (a few hundred $ saved on underfloor could be spent tuning your car for instance).
cheers,
chris.

Re: Environmentally friendly underfloor insulation 

I would line the underside of your floor and fill the cavity with wool batts.
High R-value, low embodied energy and locally made!

Re: Environmentally friendly underfloor insulation 

Hi Fiona,

We would be happy to help. We manufacture a wool insulation product (for ceilings, wall and underfloor) in Nelson using wool that is a by product from teh carpet manufacturing industry. www.latitudeinsulation.com

Re: Environmentally friendly underfloor insulation 

go to www.terralana.co.nz

Re: Environmentally friendly underfloor insulation 

Hi
I visited Terra Lana's factory in CHCH recently and was impressed. Good product - plus a friend had it installed in her home as part of Canterbury's clean heat project and is more than happy. They do ceiling/wall batts, underfloor batts with foil and also lagging for pipes.
Ruth

Re: Environmentally friendly underfloor insulation 

Hi, I'm new to New Zealand and this website. We are planning to build a straw bale house when we can afford to buy a plot of land. We have settled in Rangiora, North Canterbury. Could you tell me where Terra Lana's factory is so I could visit.
Great site by the way - great to know there are permies and eco warriors here!

Re: Environmentally friendly underfloor insulation 

There details are as follows:

55 Francella Street
Bromley
Christchurch

Ph: 0800 485 262
Fax: 03 982 0212

Or have a look at their web site:

http://www.terralana.co.nz/contact-us/

Re: Environmentally friendly underfloor insulation 

I used recycled polystyrene blocks from PolyPalace in Porirua (Wgtn). They mechanically render chunks of polystyrene back into beads, then steam them into new blocks for underfloor insulation. I'm happy with the end result.

Re: Environmentally friendly underfloor insulation 

Hello Fiona,
Do you have some interests in Bamboo flooring ? It seems to be the most eco-friendly flooring materials right now.
We are manufacturer of this products. You can contact me by MSN: ecobambooproducts@hotmail.com

WWW.ECO-BAMBOOFLOORING.COM

Allan

Re: Environmentally friendly underfloor insulation 

I did a lot of research when I was deciding on what underfloor insulation to put in. Across the board insulation is a double edge sword.

Choose a product that lasts. Gaddman recommends foil, but I wouldnt go near it for the sear fact that its insulation value is based on its reflective abilities so whilst the product will last a long time its insulation value dies once it has a film of dust on it. And for underfloor its only a couple of years before you have to clean it or replace it. The monetary saves is short term.

You also need to keep in mind how its installed, because once you get another tradesman in they dont care about how their treating your insulation. Your investment can be damaged and youll be lucky if they fix it.

Go with something that still leaves your joists exposed as well as any wire work running along them.

Installing yourself, be careful if using staples (used to secure foil, batts, and strapping). There are a handful of people who have electrocuted themselves not being careful. And you only get one chance.

Think of what you need longterm. Selling your house, allergies, budget, it all counts towards what your final decision will be. There are so many products, dont get swayed by a salesman.

Useful websites: www.eeca.govt.nz, www.consumer.co.nz,

Even local councils are getting in on the having an opinion act. So check it out.

Another safe guard is to also choose a product that is BRANZ appraised. This is an independent body that tests products to ensure the claims the manufacturer makes is true.

Goodluck Fiona, or anyone else looking to insulate.

Re: Environmentally friendly underfloor insulation 

there are three ways heat is lost:
1 convection, ie air movement, so seal all gaps.
2 conduction, ie through the material, that is why we use stuff like batts because they are mostly air and cannot conduct heat like say metal does.
3 radiation, which is the radiant glow you get from an open fire or even the sun, and being radiowaves it can pass through materials. this can only effectively be stopped by reflection. generally i think about 20% of heat loss is radiant and the other two are 40% each. tin foil only prevents radiant heat loss (unless you have a lot of air gaps as well that it seals). so even if it is 100% efficient it is not going to make much difference to your overall heat loss from the house if 10% is through the floor! so i would say it is waste of resources on its own!

this argument would suggest that the terralana product is best which lines wool with tin foil on the underside. but woolbloc argue that the wool should be allowed to breathe. is that really necessary? is condensation likely to be a problem and if so can it be solved with drip holes along the centre like the old looped tin foil?

david trubridge

Re: Environmentally friendly underfloor insulation 

Hello David,

As post fitting under floor foil insulation is difficult, and Wool Bloc recommends support (although there is confusion in their brochure on this matter), I suggest the following:

Cut a sheet of perforated foil 150mm wider than the bat width and fold 75mm down each side.

Fit the wrapped bat into position with the foil uppermost – using a 93mm bat, the void left above the foil would usually be about 50mm or greater giving a combined R2.6 approximate value. This gives the best combination to reduce radiation and conduction.

A web strapping would support the underside of the bat by being tightly stretched and stapled to the underside of the joists (first, switch off the electric power in case you hit a wire).

I note that Wool Bloc floor bats can be stapled in place without support webbing and the manufacturer states that foil in not used so that the bat can absorb and release water vapour, but my experience suggests that damp insulation losses it’s performance and is hard or impossible to completely dry again, so I would use the foil unless anyone can convince me otherwise.

I have not installed using this method but would anticipate no problems and would welcome any comment for or against.

Rex
(We have truth – just know that we do not have all the truth)

Re: Environmentally friendly underfloor insulation 

thanks rex

i have just heard from teralana that they do not make the wool+foil product any more. they now have a composite layered bat with a dense, hardwearing, polyester layer on the bottom. so i guess that answers the question about using foil as well, if they have stopped using it!

i am not convinced that your suggestion of using both foil and wool (with the foil on top) is worth the effort, given the small amount of heat loss prevented by the foil and the fact that it is not protecting the wool.

david

Re: Environmentally friendly underfloor insulation 

I'll chip into the debate...
Batts are not a conductive insulator, they act to trap air in pockets too small to allow convection to occur. They slow air movement.
Under floor is complex. Heat rises, so it naturally does not want to travel downwards through your floor, unlike ceilings where it's just dying to get out.
Heat conducts through the flooring and is then lost via two mechanisms.
1 Radiation direct to surrounding surfaces.
2 Wind wash as the breeze under the house carries away the molecules of air that are trying to cling to the underside of the flooring. It's really a type of conduction if you think about it in detail.
I suspect that #2 is the most important, so I throw my hat with the product that creates a still air zone under the floor.
Batts won't do that, unless they are in a closed cavity.
Polystyrene probably wont do that. (I don't like polystyrene anyway it's not nice stuff)
I'll pitch for bubble type foil under the joists CAREFULLY fitted to create the still air space. Pay particular attention to the perimeter where the joists end.Deluxe would be batts between the joists as well.
The foil must be insulated bubble type to slow the thermal gradient (after all foil is an excellent conductor) and ensure the dew point (and thus condensation) occurs UNDER the foil i.e. outside.
The result should be an airtight and dry cavity, the reflectivity (or otherwise) of the foil is probably of little importance. There is the further gain of it acting as a vapour barrier to rising damp, a bigger health and comfort issue than is generally acknowledged.
R-ratings alone do not factor in wind-wash or moisture movement, so don't rely on that alone.
A lot of houses also have far too much underfloor ventilation. Slatted skirting around the outside lets too much air flow. You only need a few air changes a day to take moist air away. You only need a few gaps to achieve that.
Don't forget carpet too, you don't see kids lounging on a wooden floor now do you, they aren't stupid, they know conduction when they feel it.
Stay snug!

Re: Environmentally friendly underfloor insulation 

I would also like to chip into the debate. The last answer is consistent with my beliefs too about the still air gap. I sell a wide range of insulation around NZ through 0800 206 2879 and I gather a lot of information and love to read about this stuff.
I do agree with aspects of other posts too tough. My pick that I have installed under my home is Autex Underfloor blanket stapled to the underside of the joists to give air gaps. It is made from recycled PET (coke bottles) right here in NZ. It is self supporting unlike most other batts and I see one of the wool batts mentioned above have added polyester to their recipe for this reason. With this blanket stapled to the underside of the joists in perpendicular directions to the joists we get this big stagnant air gap and you can actually pry the two edges at the joins apart put your hand up there and feel the warmth. I have been under many homes where you can actually feel the warmth that has come from the house and this is what it's capturing. The r rating of this system is typically up to R2.6. I agree anything foil must be performated for the timber to be able to breathe. I don't like polystyrene as it amplifies sound like a drum when it has a cavity. Polyester actaully reduces the sound and this made a big difference to the sound and feeel of the room as soon as we installed the product. As for value for money this seems to be unbeatable at around $11.40 per m2 DIY, compare this to any other products around considering you are getting R2.6 (we also have an R2.3 system for $9,20 per m2). I hope this helps I am happy to share more imformation. Regards Carla

Re: Environmentally friendly underfloor insulation 

carla thanks for your input - there is one bit of mis-information i need to correct. when you put your hand inside the insulation and feel warmth, that is not trapped warmth as you assert. it is the warmth of your own hand, because the insulation prevents it dissipating as much as it does in the air!! put your hand on a block of polystyrene and a block of steel. the steel will feel much colder because it dissipates your warmth, while the poly will feel warm. but they are both at the same room temperature!

Re: Environmentally friendly underfloor insulation 

Hi NZ - thank you for all this info. I'm an ex-pat Canadian now living in the desert Southwest (New Mexico, USA) who found this blog while searching for info on subfloor insulation. All your posts have educated this little ol' lady. Blessings to you all... Siridharma

Re: Environmentally friendly underfloor insulation 

Under floor insulation is pretty good for healthy and energy saving .
Seems far from our country.
Though we export a lot .but we never use it for our builing .

Tian . Twitter: tianmm

Re: Environmentally friendly underfloor insulation 

Most of the underfloor insulation that is available seems to have an R-value of only around 1.4 or so. I would have thought it would make sense to fill the whole space below the floor to the bottom of the joists with the same stuff used in the ceiling (say R2.6).

To support the batts etc would breathable building wrap do the trick without getting condensation on the top of it?

Re: Environmentally friendly underfloor insulation 

I used R3.5 batts for mine, mainly because I had bought a cheap lot. They were slightly fatter than the joists but went in nicely without too much compression.

They were held in place with plastic strapping at about 300mm intervals and then foil was used as a protective cover and over bearers etc. Foil was used because I wanted something fairly tough for a variety of reasons. I did ponder over the condensation issue but decided that, in my area, I didn't believe the under-house temperature would be low enough, long enough to be an issue.

After the insulation and ground sheet were in place for a while I noticed the floorboards tended to "creak" significantly more which I took to indicate an actual drying of the floor area to the top. I might be reluctant to use foil over a moisture barrier type floor surface like lino. The only problem with building wrap might be allowing moisture from the ground to travel into the floor via vapour?

Having said that, putting batt insulation under floor joists is literally the job from hell due to dust from the batts dropping down on you etc.

Re: Environmentally friendly underfloor insulation 

You're a brave man using fibreglass batts. I've given up on them entirely after using polyester just the once. I'm not sure that having a little bit of water vapour coming up through building wrap would be any worse than what we have at the moment and would at least let any moisture out again. I think I'll do a couple of test areas this winter and see what happens with each option.

Re: Environmentally friendly underfloor insulation 

After reading all of the comments I find it hard to believe that only 10% of heat is lost on a timber suspended floor.

I looked into all of the options, even had the EECA people give a quote to insulate a 110sqm house underfloor and ceiling.
They wanted to use greenstuff underfloor with a R value of 1.6 and greenstuff R 2.6 in the loft

Total cost after subsidy......$3400

I did some research and found that once wind blows across the greenstuff underfloor the insulation value almost drops to 0 so I looked for a better alternative also not wanting to pay $3400

I came across Poly Palace in Porirua, they make a 100mm polystyrene plank made to exactly your dimensions for the underfloor The R value is 2.5, I paid $960 for enough planks to cover 110sqm

The floor is so warm now that the dog no longer wants to get on the couch, when she gets up from laying on the floor the area where she was is so warm.

I have also used the loose beads from them also and have blown these into all of the walls.

Our heating is a Fujitsu Cartridge heat pump of 12KW capacity that is ducted to the other end of the house using one of the four outlets with rectangle to 200mm round trunking exiting in a 200mm outlet.

We are at the base of Mount KauKau with a temperature outside of 2 degrees last Thursday the Lounge was 24 degrees and all 3 bedrooms, bathroom and toilet were 18 degrees.

Heating the house to this temperature the heat pump is drawing 2KWh of power checked with my smart meter and Genesis energy monitor online.
At night the heat pump has a set back temperature of 18 degrees of which it draws 400watts per hour through the night, the system goes of at 6:30am then comes back on again at 3:30pm to heat the house before we get home.

It just goes to show that a 1980s house can be bought unto modern standards with a bit of work.

Re: Environmentally friendly underfloor insulation 

So the planks went between the joists or across the top (perpendicular) ? Across the top, foil backed poly, is a method I read on the Building Science website. Particularly good for very cold climates as there is no thermal bridging from the joists and the joists stay warm so no fear of condensation.

Can't say I noticed a great difference when I did my floor but I had carpet mostly so floor fairly warm. Still have a bare timber area to do which certainly does feel cold in bare feet!

Re: Environmentally friendly underfloor insulation 

Yes the planks went between the joists.
The planks are not foil backed but my underfloor already had foil so I laid the planks over the top.

I cannot emphasis how good these planks are, the wife now takes her slippers of and puts them on the floor as she says her feet get too hot.

I can see the reason the installers use greenstuff as it would not take very long to install.
Putting in place 110sqm of poly planks is a big job, not too bad where there aren't any cables or pipes, but very time consuming where there are, I would say it took me 2 solid days to do right.
If you do use this system make sure all planks are pushed hard against each other so no gaps, very important.
And tape brown paper over all cables so that the polystyrene is separated from them or the plasticiser will leach from the cables making them brittle.

can take pics if anyone is interested.