Insulation for new house build

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nofam

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#190636 7-Jan-2016 10:30

Hi guys,

What's the current thinking on insulation brands and R-values? I'm a big believer in passive heating through good insulation, which I think is important given I'm building in Dunedin, and the living area/kitchen/foyer will have a polished concrete floor with 2.7m stud.

The slab will have two 50mm layers of polystyrene insulation underneath, and all glass in this area will be thermally broken, argon-filled and Planitherm low-e. The rest of the house will be 2.4m stud, with thermally broken, argon filled glass. Cladding is to be Rockcote over AAC.

Downlights are planned to all be IC-F rated to minimize heatloss though insulation gaps, and I'm keen on doing at least a R5.0 in the ceiling?

Keen to hear thoughts on reducing noise between rooms too - am I best to use noise-reducing batts, or just look at double-lining with gib?

Any questions/suggestions welcome!!

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#1464986 7-Jan-2016 10:49

Good to think about this :) Thermal mass is great to keep temperatures even. Don't forget to insulate edges of the slab. Consider window sizes and locations - you want as little solar gain as possible in summer, as much as possible in winter - large eaves help with this. House direction and room planning will help.

Unsure how effective noise insulation with one wall and batts is. If you want it really quite I wonder if double walls is useful - probably overkill.

How much more expensive is triple glazed? Lots of heat escapes through windows. Are you going aluminium or PVC? Cold countries use PVC, not many use aluminium.

Consider a central ventilation system, ideally hooked up to a big central heat pump, with rooms able to be turned on and off. Think about putting ducts in the floor - I suspect big holes in the ceiling for ventilation let a fair bit of heat out.

nofam

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#1465010 7-Jan-2016 11:15

timmmay: Good to think about this :) Thermal mass is great to keep temperatures even. Don't forget to insulate edges of the slab. Consider window sizes and locations - you want as little solar gain as possible in summer, as much as possible in winter - large eaves help with this. House direction and room planning will help.

Unsure how effective noise insulation with one wall and batts is. If you want it really quite I wonder if double walls is useful - probably overkill.

How much more expensive is triple glazed? Lots of heat escapes through windows. Are you going aluminium or PVC? Cold countries use PVC, not many use aluminium.

Consider a central ventilation system, ideally hooked up to a big central heat pump, with rooms able to be turned on and off. Think about putting ducts in the floor - I suspect big holes in the ceiling for ventilation let a fair bit of heat out.

Thanks, yes, have spoken to the builder about a thermal timber break around the slab. House has quite a low number of windows already for privacy and the minimalist aesthetic we're going for on the street side, and where there are large sliding doors on the north face, the eaves are longer to block summer sun as you suggest. A really good point though, and one that I think a lot of people don't think about. All joinery is aluminium - just not really convinced about PVC here, at least in Dunedin; were I building somewhere with a bigger diurnal range (like Central Otago) I'd definitely consider it.

Have thought long and hard about central heating (underfloor water and wall-mounted radiators, central heatpump-based heating etc), but I really don't think we stack up in terms of ROI - good insulation and design as above with a couple of well-placed heatpumps should be more than enough, based on friends and family who have built recently.

My expectation (based on recent builds I'm familiar with in the same location) is that I can come home from work on a cool, sunny winters day and, through thermal gain alone, have an ambient inside temperature that's more than double the outside temperature - i.e. my living room will be around 17 degrees, but the outside temperature has never gone above 8 degrees.

timmmay

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#1465016 7-Jan-2016 11:20

PVC stacks up well in terms of price and durability. I'm replacing all my very old windows with PVC this summer. I'm convinced about their longevity.

You could be right about central heating and cooling. My older house isn't well laid out, so the heating and cooling doesn't reach our bedroom. Consider air flow for heating and cooling.

That's great if you can be 17 degrees when it's 8 degrees outside, modern houses are so much more efficient than older houses.

In summer when the sun goes down we get sun in our kitchen/dining area that heats that room up to 30+ degrees. The only way to reduce that is block the sun - opening windows is ineffective against that amount of sunlight, and air conditioning is a waste of money. So consider where the sun goes up and down.

There are other great threads about related things - wiring, conduit, a server cupboard.

billgates

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#1465021 7-Jan-2016 11:22

If you are doing polished concrete floors for north facing area then consider underfloor heating specially in South Island where it's much more colder. Unless you get a lot of sun and have some big Windows to let in a lot heat and have it blocked by Low-E glass from escaping in your North then polished concrete might not retain a lot of heat.

I am going through the same exercise as you and almost near the final design phase doing 2.7m stud on ground floor and 2.55m first floor with thermally broken, argon filled and Planitherm low-e everywhere. Cladding is also Rockcote Integra 50mm. I am going with Knauf R5.2 for ceiling insulation and R3.6 for wall insulation with R3.2 for midfloor insulation. Getting all bedrooms, home cinema double stud walls, toilets, bathroom, laundry and garage insulated as well.

Noise reducing batts and noise reducing GIB are not as effective as the marketing material states. Your standard R3.6 insulation will do just as well job of blocking some sound as noise batts for cheaper.

In order to reduce noise between rooms there are few different methods of room constructions you could look at. For me, the only room that will produce the most serious amount of noise is the home cinema room and I am making that a double stud wall construction with R3.6 wall insulation in both stud walls followed by 2x 16mm layers of Fyreline GIB on both side of stud walls with green glue (Importing from US) between this. For my entire house ceilings I have also added GIB STWC Acoustic clips to which the batten will connect to. Home cinema will however also have 2 x 16mm Fyreline GIB with green glue in between on top of this along with sealed and sound proofed solid core entry doors (x2).

Have a good read of few of the Sound Proofing Company articles below. The PDF below is a very simple to understand 11 page document on basics of sound proofing. Unless you are looking at spending few $$$ per room, you will not get absolute sound proofing from any of the rooms and this includes getting solid core doors with jamb seals etc. Sound will find a way to travel and leak and that could be from walls, ceilings and even the floor. Double GIB will be a step and be somewhat effective specially if you use green glue in between this else just stick to standard GIB with insulation between rooms which will block non speakers/sub woofers firing related noise in the bedrooms.

http://www.woodworks.org/wp-content/uploads/Acoustics_Solutions_Paper.pdf

http://www.soundproofingcompany.com/soundproofing-solutions/soundproofing-walls/

Do whatever you want to do man.

timmmay

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#1465026 7-Jan-2016 11:28

We have tile floors in our bathroom, I wouldn't have that without heating. Without heating, in winter, it's ok in shoes, not too bad in socks, and not very nice in bare feet. In the middle of summer I might turn it off, but only on the hottest days. That suggests to me concrete floors may be similar, BG probably has a good point. Not sure I'd do tiles in the bathroom again, but in the kitchen where you wear shoes anyway maybe not quite as important.

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#1465037 7-Jan-2016 11:40

I never understand this thermal mass concrete slab thing.

A huge bottomless heat sucker in the winter that is impossible to counter.

A giant oven roasting slab in the summer that is impossible to cool.

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billgates

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#1465039 7-Jan-2016 11:46

joker97: I never understand this thermal mass concrete slab thing.

A huge bottomless heat sucker in the winter that is impossible to counter.

A giant oven roasting slab in the summer that is impossible to cool.

This is where size/length of Eaves do the magic. This is the hard part. Calculating the right size/length of eaves required to block sun in summer when it's higher but allow sun in winter when it's lower.

Do whatever you want to do man.

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#1465042 7-Jan-2016 11:48

One would be assuming the sun is heating the concrete slab in the winter ... or is it a giant heat sink and sucks all the heat up in the winter?

And summer roast ... yikes.

billgates

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#1465047 7-Jan-2016 11:54

Concrete slab has a very good thermal mass property. When it gets heated up (via sunlight or under floor heating), it retains the heat and starts to slowly release this over the course of next few hours. Usual trick in winters is to turn ON underfloor heating at night when it's cheap electricity and turn it OFF in the morning. By now the concrete slab starts releasing the heat it has stored for next few hours during morning and afternoon so free/cheap heating during this period. In summers, if the slab is not exposed to any direct heat then it will not store any for it to be a summer roast.

Do whatever you want to do man.

jonathan18

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#1465076 7-Jan-2016 12:24

What's it like walking on an unheated concrete slab in the cold months? I'd imagine even in places with relatively benign winters it's far from pleasant, but surely in a climate like Dunedin even if the slab is thermally broken it's going to be @#$%#ing freezing?

I'd never consider having tiled or concrete flooring in my main living areas of the house unless I can be assured they'll not be cold in winter, and I'd assumed such assurance would only come with underfloor heating!

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#1465130 7-Jan-2016 13:39

No it's not a concrete floor, it's the concrete slab under the house on which the house is built.

I'm not convinced it heats the house in winter and doesn't toast the house in summer.

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timmmay

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#1465132 7-Jan-2016 13:42

joker97: No it's not a concrete floor, it's the concrete slab under the house on which the house is built.

I'm not convinced it heats the house in winter and doesn't toast the house in summer.

Thermal mass is generally good. In winter you heat your house each day and it slowly heats up, releasing heat if the ambient is lower. In summer it sucks up heat, reducing the interior temperature. It could make heating the house from scratch take longer in winter from dead cold.

It's a good buffer to prevent extremes.

jonathan18

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#1465139 7-Jan-2016 13:54

joker97: No it's not a concrete floor, it's the concrete slab under the house on which the house is built.

I'm not convinced it heats the house in winter and doesn't toast the house in summer.

Yeah, I realise it's the slab that's acting as a heat sink.

I had assumed that to be of full value to act as a heat sink the slab needed to be exposed (so, in practice, a concrete floor!) or, if covered, done so with a similar material (eg tiles). Is this not the case? Ie, can a concrete slab absorb the heat totally adequately through flooring such as carpet?

Anyway, the OP has clearly stated the house will have polished concrete floors, hence my concern regarding a lack of underfloor heating.

mattwnz

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#1465142 7-Jan-2016 13:55

nofam: Hi guys,

What's the current thinking on insulation brands and R-values? I'm a big believer in passive heating through good insulation, which I think is important given I'm building in Dunedin, and the living area/kitchen/foyer will have a polished concrete floor with 2.7m stud.

The slab will have two 50mm layers of polystyrene insulation underneath, and all glass in this area will be thermally broken, argon-filled and Planitherm low-e. The rest of the house will be 2.4m stud, with thermally broken, argon filled glass. Cladding is to be Rockcote over AAC.

Downlights are planned to all be IC-F rated to minimize heatloss though insulation gaps, and I'm keen on doing at least a R5.0 in the ceiling?

Keen to hear thoughts on reducing noise between rooms too - am I best to use noise-reducing batts, or just look at double-lining with gib?

Any questions/suggestions welcome!!

Does the expense of low e, and argon filled glass outweigh the savings you would make in heat loss? As a lot of the heat is still out the windows, you can actually reduce the heat loss more by reducing the window sizes.

Edge insulation is more important IMO than insulating under much of the slab, as most is out of the edges. A timber thermal break doesn't provide much insualtion, as timber isn't a great insulator. XPS is probably the best thing to use for edge insulation.

mattwnz

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#1465145 7-Jan-2016 13:59

timmmay: PVC stacks up well in terms of price and durability. I'm replacing all my very old windows with PVC this summer. I'm convinced about their longevity.

You could be right about central heating and cooling. My older house isn't well laid out, so the heating and cooling doesn't reach our bedroom. Consider air flow for heating and cooling.

That's great if you can be 17 degrees when it's 8 degrees outside, modern houses are so much more efficient than older houses.

In summer when the sun goes down we get sun in our kitchen/dining area that heats that room up to 30+ degrees. The only way to reduce that is block the sun - opening windows is ineffective against that amount of sunlight, and air conditioning is a waste of money. So consider where the sun goes up and down.

There are other great threads about related things - wiring, conduit, a server cupboard.

I was speaking to a builder/ developer who builds eco houses, and he advised against PVC from his own experience. He said they just don't stack up compared to the new aluminum profiles you can now get. Also questions over low term durability with the NZ conditions. Also many people don't like the look of PVC, they have a bit of a stigma to them. They are used a lot in the UK, and don't look great when retrofitted into terraces . I would suggest visiting some house that have had them in for the last 10 years to see how they are performing, and how the owners find them. With aluminum, they are a known quantity, and durable/low maintenance. I have some anodized ones that were install 12 years ago, and they look as good as new.

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