home insulation - insulating paint?

GreenNotM

gromituk wrote:

Not at all. I'm just pointing out that your conclusion is a bit simplistic.

Gromituk - Calmgirl may have explained herself simplistically - but totally correctly..

The following is from the link I posted earlier
"HEATING & WATER: MAXIMISING RADIATOR EFFICIENCY
The placement of radiators is of great importance. The standard logic of radiator placement is that they should be placed under windows to counteract the downdraft of cold air from the window. If they are placed on the wall opposite a window they will set up a convection current in which hot air rises and sits at the top of the room and pulls cold air across the room from the window.

Well, that is the theory and it makes sense for old houses with leaky single glazed windows. The logic doesn’t apply so well for well sealed double glazed windows, especially the high performance ones in the Yellow House. There is also a stronger counter argument for not placing radiators under windows. Radiators literally pump radiated heat into objects close by- the wall behind the radiator is the hottest place in the room. If a radiator is against an external wall then that heat is going to be wasted (and, of course, windows are always in external walls!). What is more, the hottest air in the room then rises over the coldest object - the window - another source of heat loss. To make matters worse, many people have curtains over the window which drape over the radiator- so the hot air rises up and circulates uselessly behind the curtain. All in all, if you have high performance windows it's worth placing radiators against internal walls wherever possible.

The strategies we followed in the Yellow House were:


1. Where possible place radiators against internal walls. We had to make do with existing radiators in most rooms which were all under windows, and the replacement radiator in the front bedroom would only fit comfortably under the window. The new radiators for the kitchen and bathroom are both placed against internal walls with the TRV set to a high setting to encourage them to work as much as possible.

2. When the radiator is on an internal wall, it is worth encouraging it to "pump" heat into the wall behind it. This uses the thermal mass of the house to keep a steady room temperature. For the radiators placed against internal walls, the back of the radiator and the wall behind it are painted with very dark paint to encourage this storage effect.

3. The radiators on external walls need to be discouraged from "pumping" heat into the wall. All DIY stores have sheets of reflective insulation to place behind radiators. It’s expensive to do a whole house so it’s cheaper to make your own and easier to make them to the required size. Ours are sheets of thin cardboard, with old polystyrene ceiling tiles glued on (reused from tiles removed from one of the rear rooms), covered with smoothed aluminium kitchen foil. They are taped to the wall with duct tape. They are about 7mm thick- which is about right as it is important to keep as much air space as possible behind the radiator. If you can’t keep at least 2cm of air space, it’s best not to try. "

gromituk wrote:

Originally Posted by calmgirl
also many victorian houses have a very thin slate roof with no backing to it consider that spray stuff you can use

Not a good idea. Roofs do not provide any insulation anyway: it is the insulation in the loft which does the work. Lofts need to be ventilated to prevent mildew and worse. Spraying stuff under the slates merely masks leaks and encourages rot. Loft conversions utilise insulation with an air gap above it.

Here is one product And some of their site's blurb
"Q: Do you allow for ventilation?
A: Yes, most properties have openings at eaves level to promote a cross flow of air, these are maintained and improved if necessary.

Q: Does it cause condensation or rot the timbers?
A: No, it prevents condensation, and because it is not a vapour barrier, it allows timber to breathe.

Q: Does the system increase the weight of the roof?
A: No, very low additional loading to the roof structure being less than 2kg/m2.

Q: Is it a good insulation?
A: Yes. Significant reduction in heat loss and consequently saving on heating costs.(If required, given certain information from yourselves such as heating cycle and type of heating fuel used, we can calculate estimated payback periods).

Q: Will we still get condensation problems?
A: No. Elimination of underside roof condensation.

And another advice site says...
" As for installing foam insulation in the attic, I would be very careful. It is possible to spray foam directly to the underside of a roof. This can keep the attic space very comfortable indeed. Consider doing this if the heating and cooling equipment must be placed in an attic space. If this equipment and the connected ductwork are exposed to extremes of hot and cold, it can lead to higher energy costs. But keep in mind that the attic is often the sole pathway for excess interior water vapor to leave a home. Some foam insulations may significantly block the movement of water vapor. In addition, be sure the foam is the open-cell variety so if there is a roof leak, the liquid water passes through the insulation and is not trapped against the wood roof sheathing and framing lumber. "

The roof itself as built may not provide insulation but it is the source of cold/heat into the loft space reducing the temp variations in the loft with the correct materials and ventilation from the eaves allows the loft to be used for storage and reduces the need for insulation on the floor of the loft space, but of course the loft floor needs to be insulated to stop the warm air raising from the habitated rooms and stopping the vented colder air cooling the ceiling of the rooms below.

gromituk wrote:

Quote:
Originally Posted by calmgirl
And you say you have new rads. are they under the windows as this is the most inefficent way to heat a house as 40-50% of the heat goes through the glass.
Can you please provide a reference for this? The reason why radiators are put under windows is to counter the down-draught from the cold window surfaces - they do lose more heat per unit area than walls - but this figure seems greatly exaggerated to me.

Again from the yellow house pages - and the science for the above - please exmine the u values and consider the fact you are applying heat directly to the windows and external wall. Many more references are available.

http://www.theyellowhouse.org.uk/themes/insula.html#in11
use low heat loss windows. There is an enormous difference between different types of windows- the chart below shows the level of heat loss (called the u-value) of different types of frame and glazing:

" U-VALUE
(heat loss per square metre)
Single glazed, solid metal frame 5.6
Single glazed, wood frame 4.3
Double glazed, solid metal frame 3.9
Double glazed metal frame with thermal break 3.2
Double glazed wood frame 2.5
Double glazed wood frame, argon and low-e glass 1.6
Explanation of u-value...(below)


As these figures show, the kind of frame is almost as important as the glass. Double glazed windows with solid metal frames are scarcely much better than single glazed windows with wooden frames. Many of the aluminium replacement windows fitted in the 1980s, including those in the Yellow House, are of this type and may have severe condensation problems on the inside of the frame "

"Brick & concrete block Cavity wall 0.6
Tiled roof with no felt 0.53
Tiled roof with felt 1.9
Single glazed window 4.5-5.5
Double glazed window 2.5-3.5
Solid timber door 3
U values for Windows.. (above) "

The u-value gives the heat loss of one square metre of a specified thickness of combined materials. In each case the value given is for a difference on temperature between the two surfaces of one degree centrigrade.

996ducati

GreenNotM wrote:

Gromituk - Calmgirl may have explained herself simplistically - but totally correctly



Again from the yellow house pages - and the science for the above - please exmine the u values and consider the fact you are applying heat directly to the windows and external wall. Many more references are available.

http://www.theyellowhouse.org.uk/themes/insula.html#in11
use low heat loss windows. There is an enormous difference between different types of windows- the chart below shows the level of heat loss (called the u-value) of different types of frame and glazing:

" U-VALUE
(heat loss per square metre)
Single glazed, solid metal frame 5.6
Single glazed, wood frame 4.3
Double glazed, solid metal frame 3.9
Double glazed metal frame with thermal break 3.2
Double glazed wood frame 2.5
Double glazed wood frame, argon and low-e glass 1.6
Explanation of u-value...(below)


As these figures show, the kind of frame is almost as important as the glass. Double glazed windows with solid metal frames are scarcely much better than single glazed windows with wooden frames. Many of the aluminium replacement windows fitted in the 1980s, including those in the Yellow House, are of this type and may have severe condensation problems on the inside of the frame "

"Brick & concrete block Cavity wall 0.6
Tiled roof with no felt 0.53
Tiled roof with felt 1.9
Single glazed window 4.5-5.5
Double glazed window 2.5-3.5
Solid timber door 3
U values for Windows.. (above) "

The u-value gives the heat loss of one square metre of a specified thickness of combined materials. In each case the value given is for a difference on temperature between the two surfaces of one degree centrigrade.

Those U values shown there dont actually comply to the current building regs in the UK?

The maximum U values are as follows:

Wood/PVCu frames = 2.0W/m2 k

Aluminium/Steel =2.2W/m2/ k

These are all fully explained in Part L of the building regs which is now being revised to become even tougher.

The upshot of this is that modern aluminium/pvc windows are now able to offer thermal performance that wasnt dreamt about 10-15 years ago. Hence the popularity of our curtain walling which is simply put whole walls of buildings made of glass. The advances in glass performance & thermal technology in framing has allowed this to become part of modern commercial buildings.

As regards positioning of radiators, a huge project is underway at the moment to build lots of new schools. The radiators will all be mounted under the windows & fed cold air from the outside which will collect the warm air from the rad & as we know the heat will then rise across the room and warm the class as it convects.

gromituk

GreenNotM wrote:

Gromituk - Calmgirl may have explained herself simplistically - but totally correctly..

You seem to have misunderstood what I was saying, and picked up on one thing to the exclusion of all others.

I did NOT say that there is no merit in the radiator positioning argument. What I did say was that she cannot possibly conclude from a comparison with next door's house and its gas bills that this is what is responsible for the difference, because there are so many other factors to take into account.

Is that crystal clear now?

GreenNotM

loreleicat wrote:

Help needed. We are lucky enough to live in a relatively large detached Victorian house but the pennies are tight now. The first winter we moved in, a bowl of water in our front room froze. We have done all the usual over the last 10 years - double glazing, new back and front doors, hardboarded and carpeted the floor, new radiators, loft insulation but still the place is just really hard to keep warm.

The OP was asking about an old house with double glazing upto 10 years old and an old roof.

The figures you give are for new buildings. New schools ( to replace the old inefficent victorian/edwardian/60's schools ) are occupied only during the day and not designed for 24/7 living - taking the out side air is for ventilation as no doubt the building will be draft free and have windows designed to be opened for emergency exits if at all, together with heat exchange taking +70% of the heat from the exiting stale air. Radiators on a single skin external wall are inefficient and will not help the OP heat her Victorian detached des res....

Calmgirl and myself are trying to offer practical help (from our own experiences ) in the actual situation she is in - not tell her how nice rebuilding her house will be if she applied the new building standards - as we are unable to help with the request for thermal paint. But we have wandered from the point...and not helping the OP ... so I will add no more to this wonderful discussion ...

slobbery

I think this:



is what the OP was looking for.
I can't seem to link to the actual product and don't know how to submit an image. Is there a guide on here as to how to do these? i can't find one.

slobbery

managed link (above) to pic of product but still can't add it to page!

dc

There seems to be a few red herrings being posted and exactitudes argued about, how long was the original string?


From memory the paint referred to contains miniscule plastic balls of gas, maybe air, and that gives the insulation.
How cost effective this paint is is anyones guess, as I think being a Nasa development it will be expensive.

A house is a leaky box to heat.
Heat rises
Heat loss is proportional to temperature differences, and the type of materials the house is built of.
Draughts cause discomfort.
So draught proofing and insulation ( especially behind radiators) is more important than the position of radiators in the big scheme of this. Rooms have a fixed heat loss proportional to the temperature of the respective surfaces. The positioning of the source is more a comfort/spacial issue. eg a radiator on an internal wall, with a big leather couch pushed up to it is of little use, in the radiation and convection side of heating :rolleyes2

Skirting heating was a good solution, not taken up by us Brits, but now being replaced by underfloor to which has the same "window" argument, after all underfloor is outside too.

One criticism about what calmgirl says is that the cavity is ventilated, so air, not trapped. Hence the need for cavity insulation.

dc

grumbler

Solid Wall Insulation

Dry Lining

996ducati

GreenNotM wrote:

The OP was asking about an old house with double glazing upto 10 years old and an old roof.

The figures you give are for new buildings. New schools ( to replace the old inefficent victorian/edwardian/60's schools ) are occupied only during the day and not designed for 24/7 living - taking the out side air is for ventilation as no doubt the building will be draft free and have windows designed to be opened for emergency exits if at all, together with heat exchange taking +70% of the heat from the exiting stale air. Radiators on a single skin external wall are inefficient and will not help the OP heat her Victorian detached des res....

Calmgirl and myself are trying to offer practical help (from our own experiences ) in the actual situation she is in - not tell her how nice rebuilding her house will be if she applied the new building standards - as we are unable to help with the request for thermal paint. But we have wandered from the point...and not helping the OP ... so I will add no more to this wonderful discussion ...

So as my original post pointed out the U values quoted are incorrect on an old house,new house or an airport!

The second point regarding positioning radiators was to demonstrate that the latest projects are having the rads under the windows because the same principle still applies. Draughty windows let cold air in passing radiator heat which is warmed & rises then drops once cool to heat the room. Therefore the conventional wisdom is that rads are fitted under windows for this purpose. :beer:

loreleicat

Well here's my "snakeoil" if anyone wants to give an opinion......

http://www.thermilate.com/insulating_paint_additive.shtml