Author Topic: Insulation - UK / US  (Read 3751 times)

kyanamerinas

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Insulation - UK / US
« on: May 01, 2014, 10:41:45 AM »
MMM talks about insulating to R50 in his latest post, what does that really mean? In the UK they usually talk about depth when it comes to insulation and the current recommended amount seems to be 270 mm.
A quick google suggests R50 may equate 470 mm (I know this really depends on the material being used). That is a big difference! Have I got that right and if so, any ideas on why the difference (probs just as simple as difference countries, different recommendations).
Currently buying a house without any loft insulation and wondering how much to add.

nereo

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Re: Insulation - UK / US
« Reply #1 on: May 01, 2014, 11:02:47 AM »
The "R" value is just a measure of thermal resistance.  Read about it here:
http://en.wikipedia.org/wiki/R-value_%28insulation%29

The higher the R value, the more thermal resistance you have per given unit of thickness.  In layman's terms, the higher the R value the better for insulation purposes.

Every substance has a different R value (Insulating foam, spray foam, cellulose, packed sawdust, etc).  There are trade-offs for every kind (for example, closed-cell spray foam has an extremely high R value, but is much more expensive than cellulose. Cellulose is cheap, but you need something like 25cm of it to insulate as well as just 3cm of spray foam).

sherr

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Re: Insulation - UK / US
« Reply #2 on: May 01, 2014, 11:09:24 AM »
Well I don't know about the UK system, but the R system is a way of measuring how hard it is for the heat to leak in or out. The higher the R value, the more insulated you are. As you say different materials can have a huge difference in how efficient they are at insulating, so 270 mm of one material may be equivalent to 470 mm of another. The R system is designed to allow you to easily compare them, R50 insulation always insulates exactly as well as any other R50 insulation, regardless of the amount or type of material required to achieve it.

R50 is pretty high on the scale of normal recommendations for the US too. Having more insulation can never hurt, it may just be unnecessary. The more insulation you have the easier it will be to keep the house warm in the winter and cool in the summer. If you live in a climate where you don't need to do either for 95% of the year, then it's probably a waste of money to have any insulation. How much it makes sense for you to have depends on your climate, temperature preferences, and cost of heating / cooling.

kyanamerinas

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Re: Insulation - UK / US
« Reply #3 on: May 01, 2014, 11:20:10 AM »
ok. that certainly helps and gives food for thought once we have the house. we have a pretty moderate climate, not often below freezing and rarely above 30oC so probably don't need to go as far as R50.

nereo

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Re: Insulation - UK / US
« Reply #4 on: May 01, 2014, 11:37:59 AM »
ok. that certainly helps and gives food for thought once we have the house. we have a pretty moderate climate, not often below freezing and rarely above 30oC so probably don't need to go as far as R50.
R50 is high just about anywhere.  In most places you are on solid footing if you have an R16.  BUT, most forms of insulation are so cheap that the main expense is the labor in putting it in (yours or a contractor's).  For that reason I typically put as much insulation in as the space will hold.  Going from 10cm to 20cm of insulation might add only a few hundred dollars, which you can recoup in a few years. 

kyanamerinas

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Re: Insulation - UK / US
« Reply #5 on: May 01, 2014, 11:53:38 AM »
ok. that certainly helps and gives food for thought once we have the house. we have a pretty moderate climate, not often below freezing and rarely above 30oC so probably don't need to go as far as R50.
R50 is high just about anywhere.  In most places you are on solid footing if you have an R16.  BUT, most forms of insulation are so cheap that the main expense is the labor in putting it in (yours or a contractor's).  For that reason I typically put as much insulation in as the space will hold.  Going from 10cm to 20cm of insulation might add only a few hundred dollars, which you can recoup in a few years.

yeah, we'll certainly do the maths and put in as much as pos whilst leaving sufficient space for the loft still to be used for storage (although i doubt we'll need this ourselves).

Greg

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Re: Insulation - UK / US
« Reply #6 on: May 01, 2014, 01:49:53 PM »
Here in Thurston County, Washington, USA, we have a pretty strict energy code.  Now requiring R-38 in ceilings, R-21 in walls, R-30 in floors.  R-8 on ductwork and R-10 for slab floors.  R-4 for pipes.  R-10 for pads under water heaters.  And so forth.  Now also requiring blower door tests for air leakage.

nereo

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Re: Insulation - UK / US
« Reply #7 on: May 01, 2014, 02:46:36 PM »
Here in Thurston County, Washington, USA, we have a pretty strict energy code.  Now requiring R-38 in ceilings, R-21 in walls, R-30 in floors.  R-8 on ductwork and R-10 for slab floors.  R-4 for pipes.  R-10 for pads under water heaters.  And so forth.  Now also requiring blower door tests for air leakage.
Wow, Go Thurston!  I know a lot of people hate building codes, but I think we'd be better off as a planet if every single new structure that was built had to adhere to similarly strong codes (with respect to the local environments, of course).  Half of all the energy we use goes towards heating and cooling buildings.