[Greenbuilding] Insulating shallow crawl spaces

John Bone johnbone at gateshead.plus.com
Fri Apr 13 03:41:11 CDT 2012


Hi,
In the UK, for example, today's Central London air temp is 14-16 C and we  
all think that this is a nice warm day. So the use of A/C (Air  
Conditioning) in houses is just totally unheard of,... no one has it.
Frankly, if you see Air Con on a home then you know that person is a  
migrant.

I live 30 miles out on a commuter rail line (30 mins into Euston, London -  
$50 a day, including hop-on hop-off all public transport (bus, rail,  
water-bus, tube, trams, surface rail) in Greater London.

Here in Leighton Buzzard (Bedfordshire), it is 12 - 14 C (at 10am) and  
again I feel no need for a wooly jumper or to put on my homes central  
heating. The coldest day of the current year (for my town) so far has been  
minus 10 C (but central london has only just had minus 1 C).
However, I am working from home today - I work as a Fire Risk Assessor and  
Building Code Advisor at a not-for-profit social housing provider (who  
have 16,000 flats and street homes in their stock, with 1100 blocks of  
apartments).

I own my own home, it is "new" (2005) and has 12 inches of Mineral Fiber  
Roll/Quilt in the roof space (above the ceiling), and 4 inches of   
Isocyanurate in a solid floor (ground bearing) on a reinforced raft  
concrete foundation. The external walls are 4 inch brick with 3 inches of  
insulation (mineral wool) in a filled cavity, and an internal lightweight  
concrete block leaf (4 inch thick), with a 1/2 inch dry-rock wall panel  
board (plasterboard) on dabs (1/2 thick) of plaster adhesive, to give a  
further air gap.
By law (Building Code 2000) the windows and door are all UPVC double  
glazed ("k" glass) (ISO 'U' value 1.9 W/m2K).
By law (Building Code 2000) these double glazed Doors and Windows are  
limited to an area less than 15% of the homes floor area.
By law (Building Code 2000) the House has to be less than 10 M3/M2/S for  
air-tightness and had to be pressure tested.

This is indeed a long way from a Passive House, but is current fair  
practice. Todays (2010 Building Code) is now building to 25% higher  
thermal insulation standards.

Gas Boilers have to be A or AA rated - beter than 90% efficient. Forced  
Air heating is not used here. Everyone's Central Heating uses hot water  
radiators or (rare but growing) hot water underfloor heating loops.

If your home is off-grid boilers use LPG or Oil - a few new houses are  
using air-to-air heat pumps, and a few are using ground source heat pumps,  
but you are talking about 1% of new homes. There is no 'tax breaks' for  
building a higher efficiency home.

This may change as the national government is talking of a "green deal",  
where efficient boiler retro-fitting, extra insulation and even  
photo-voltaic panels, would be funded by the local energy companies and  
the home-owner would be locked in to their fuel use in return for 10, 15,  
or longer years.

We expect our buildings to get damp and we ventilate and limit moisture  
movement, to protect the building fabric. Really Hot days (over 20 C) are  
rare perhaps 30 a year, so A/C is not cost effective, nor required.

In the Heat Island of Central London, A/C is used by offices & shops - but  
their are strict limits on its use (Building Code) natural ventilation,  
and non A/C mechanical ventilation is far easier to get approval for.

Most older houses in England (UK) have no underfloor insulation and have  
suspended timber floor and underfloor natural air venting to allow the  
house to dry during the summer. The UK Building Codes have only required  
ground level floor thermal insulation since 2000. There was no thermal  
insulation requirements in the UK Building Codes before 1976.

Central London (the six inner London boroughs) have only had Building  
Codes requiring thermal insulation for houses and buildings since 1985.

Yes, no where in the UK is more than 78 miles from some part of our  
surrounding sea coastline. However, we do not see ourselves as being in a  
very humid climate.

The EU (European Union) Parliament has pushed high insulation measures and  
the UK national government is followed these in recent revisions to the UK  
building codes. The EU has also now effectively banned the sale of high  
energy filament light bulbs.

I hope this helps.

John Bone, MBEng, BSc Hons
Fire Risk Assessor & Building Code Advisor

On Thu, 12 Apr 2012 15:04:09 +0100, elitalking <elitalking at rockbridge.net>  
wrote:

>
>> Thanks John Bone for responding to my query.
>
>
> I thought of insulation above the floor.  For me, I could live with a  
> lower ceiling height.  However, I am tasked with satisfying >my client.   
> It is only an 8' ceiling to begin with.  Since below the floor would be  
> ventilated with outdoor air, it would have a >lower Winter temperature.   
> Though the first inch would achieve the air tightening benefit, the R  
> value would still be low.  Using >Isocyanurate, 2" could give only an  
> R14+-.   I use the above the floor strategy for insulating existing  
> concrete slabs with new >wood floor above.  In that case, the ground  
> temp is much higher in the winter than outdoor air.  
>
> If this is how it is commonly done in UK, I have these questions about  
> your experience.  
>
> In hot weather do you cool your houses with AC?  If so, does the shade  
> and cooler surface of the bottom of the floor result in >pulling in the  
> warmer air into the crawl space?  Does this ever result in lowering the  
> air temp to dew point?  You say the >ventilation is sufficient to keep  
> wood dry.  I would like to understand why.  My impression of UK is that  
> the climate is fairly >maritime (humid).  
>
> Eli
>----- Original Message -----
>> From: john boneTo: 'Green Building'Sent: Wednesday, April 11, 2012  
>> 11:41 AM
>> Subject: Re: [Greenbuilding] Insulating shallow crawl spaces
>>
>>
>> Hi,
>> The English (UK) solution to this not uncommon situation would be to  
>> insulate above the floor, leaving the timber to age in a ventilated  
>> space, which will >>protect it from damp build up.
>>
>> John Bone, MBEng, BSc Hons
>> UK Building Code Official (1974-2009)
>> UK Fire Risk Assessor (2009-ongoing)
>>
>>
>>>> From: greenbuilding-bounces at lists.bioenergylists.org  
>>>> [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of  
>>>> elitalking
>> Sent: 11 April 2012 16:14
>> To: Green Building
>> Subject: [Greenbuilding] Insulating shallow crawl spaces
>>
>>
>> I have a deep energy retrofit project on an old framed house where  
>> there was no excavation for the crawls space.  The result is >>that the  
>> front, downhill side of the house has adequate room for installing  
>> insulation.  However, much of the house has less >>(18”-24”).  The  
>> floor condition is good enough that we are not considering removing the  
>> floor.  The room height is >>insufficient to consider adding insulation  
>> to the top of the floor.  How do I insulate the floor.  
>>
>> For the rest of the house, we are planning on installing new ceiling  
>> rafters parallel to the roof pitch to define 14” space to fill >>with  
>> open cell foam.  We are installing furring strips installed with 2” gap  
>> in front of old wood siding.  We are adding >>continuous 2.5” closed  
>> cell foam to fill the gap.  The old plaster is gutted.  We can fill  
>> with adhered cellulose or open cell >>foam in the 2x4 framed walls.  On  
>> another similar job, I came to the inside of the foundation to continue  
>> closed cell foam >>thermal barrier and came across the ground with  
>> closed cell foam.  All of that was covered with the high cost spray  
>> ignition >>barrier.  In hind site, with that job, I would have  
>> preferred to use rigid board insulation such as XPS.  I would create a  
>> ground >>plane with combination of digging high spots and filling low  
>> spots with crush and run (small gravel), lay one layer of extruded  
>> >>board to provide puncture protection, a layer of poly for continuous  
>> vapor barrier and another foam layer.  I put osb on top for >>cheap  
>> ignition barrier that protects the foam from traffic damage.  The whole  
>> house is provided with HRV for fresh air.  
>>
>> However, this house does not have adequate space to work in.  
>>
>> Do I need to hand excavate to a minimum clearance for the work? If we  
>> did that, I could install either of the approaches >>describe above.    
>> I was wondering if I could fill the whole space with open cell foam.  I  
>> realize that 1/2 # open cell foam is not >>a vapor barrier, therefore  
>> likely not a good idea.  
>>
>> I am encouraging my client to use a mini split heat pump to avoid the  
>> need for ductwork in the crawl space.  Therefore, I can >>define the  
>> thermal barrier at the floor plane instead of the ground.  Because we  
>> would still have moisture issues below, I am >>leaning towards ground  
>> insulation.  However, a closed cell foam application to the bottom of  
>> the framing could provide the >>vapor barrier to protect the wood.   
>> Below that the stone and concrete surfaces are not vulnerable to  
>> humidity.
>>
>> Right now, I consider the hand excavation to be the most likely  
>> scenario. Because the mini split will cool the house, I am >>against  
>> the traditional ventilated crawl spaces with fiberglass batts in floor  
>> framing because the cool shadow will pull in hot >>humid air and cool  
>> it to dew point creating humidity problems.    
>>
>> This is a common situation with old house.  I hope our list can offer  
>> some good ideas for cost affective ways of upgrading to a >>high  
>> standard.  
>>
>> Eli
>> www.conservationarchitect.net
>>
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-- 
John Bone, MBEng, BSc Hons,
Home Email: JohnBone at gateshead.plus.com
Sent from my 'Laptop' Email: JohnBone at Gateshead.plus.com {PlusNet}
Using Opera's revolutionary email client: http://www.opera.com/mail/
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