Radiator Booster - any thoughts?

don0301

zeupater wrote: »

Hi

I'm a great believer in using thermal mass as smoothing mechanism in a domestic heating environment, especially so when looking at passive heating.

In our house, at this time of year onwards a couple of days of good solar gain from low sun angles provides enough heat to remove the need for heating for at least a further day or two, with the high mass preventing the south-facing rooms from overheating.

Our GCH has been off this week due to the mild weather and all required heat has been provided by some late use of our log burner, approx 8 to 10kg of wood each day, so around 25 to 30kWh of heating. Over the week this level of heating has resulted in there being no need for heating of any form today, whether there is a requirement to light the fire tomorrow will depend on the overnight losses and what the level of solar gain is tomorrow ... low thermal mass properties have a faster response but are unable to effectively moderate and/or store heat as effectively.

HTH
Z

you should 'educate' the construction industry of this!

clearly they have got it totally wrong in energy saving techniques!

don0301

whasup wrote: »

This is the principle of thermal response. An older style house with higher mass walls will store much more heat than the opposite type of modern house. The older house warms up more slowly but also retains heat for longer (low thermal response) and the modern house warms up quickly but, as a lot of us know, cools down quickly (high thermal response). So which is the most efficient? A lot of people would have you believe that the old house is more efficient because, when the boiler starts up, you're not heating up from stone cold. But that's not really true. For the same heat source controllability is the greatest factor and it is much more efficient to have the heat there when you want it and not when you don't.

My own greatest saving in the last year is realising that I don't have to set my boiler to come on automatically for the evening period. We were often getting home at 5, 6 o'clock or later and the boiler had been blowing away since 4.00pm with nobody there. So now we just flick it on when somebody gets home. (if necessary) The high thermal response means it takes about 15 minutes to get warm and the savings are significant for that slight bit of discomfort.

really? let me introduce insulation to your argument...:D

zeupater

Hi All

I would consider that introduction of insulation should be considered as being a red-herring when considering any property which is not built to lightweight passivhaus specifications. Effectively adding an equivalent level of insulation or airtightness to either a low internal mass or high internal mass structure would be similar to adding identical complexity to two sides of an algebraic equation, they would simply cancel each other out.

High internal thermal mass simply acts as a heat-sink when there is an excess of heat and a radiative source when there is a deficit, therefore providing a temperature smoothing mechanism. I believe that high mass is good and it has suited us well for many years ... we have a property which is comfortably warm in the winter and comfortably cool in the summer .... what more can one ask for.

HTH
Z

don0301

zeupater wrote: »

Hi All

I would consider that introduction of insulation should be considered as being a red-herring when considering any property which is not built to lightweight passivhaus specifications. Effectively adding an equivalent level of insulation or airtightness to either a low internal mass or high internal mass structure would be similar to adding identical complexity to two sides of an algebraic equation, they would simply cancel each other out.

High internal thermal mass simply acts as a heat-sink when there is an excess of heat and a radiative source when there is a deficit, therefore providing a temperature smoothing mechanism. I believe that high mass is good and it has suited us well for many years ... we have a property which is comfortably warm in the winter and comfortably cool in the summer .... what more can one ask for.

HTH
Z

I would consider adding high thermal mass to a property a red herring!

So, cavity wall insulation or loft insulation is a red herring for the rest of us?

malc_b

Cardew wrote: »

Whilst it seems like a good idea, there is absolutely no evidence that reflective foil(or any of these devices) behind a radiator saves any money.

Most heat from radiators is by convection/conduction not radiation.

The area of wall behind the radiator will reach the same heat as the rest of the wall by 'heat soak'.

Place a brick in a bowl of hot water with half of it submerged and the half that is out of the water will reach the same temperature as the rest of the brick.

If foil worked, we would simply need to line our rooms with foil to keep in all the heat.

You misunderstand what the foil's purpose is. Yes radiators work mainly by convection but they are at 70C a or so and only a few cm from the wall so they warm the wall behind them by radiation as well. Heat loss is proportional to the difference between inside and outside. So if all the room, walls, air, etc is a 20C and the outside at 0 then the difference across the walls is 20C. But if the wall behind the radiator is at say 30C then the bit behind the wall is losing heat at 150% of the other parts of the wall. The foil is thus not to reflecting heat into the room or anything like that. It's purpose is to keep the wall behind the radiator cool, at the same temperature as the rest of the room.

It is a a minimal amount of heat lost overall but then foil is cheap. The simplest DIY way to do this is with a bit of cardboard cut into a fat T shape so the top of the T rests on the radiator brackets. Cover that with foil and drop it down behind the radiator.

zeupater

don0301 wrote: »

I would consider adding high thermal mass to a property a red herring!

So, cavity wall insulation or loft insulation is a red herring for the rest of us?

An excellent example of illogical selective thinking and posting there. As others can plainly see and for total clarity to yourself, please consider the text which you have obviously intentionally excluded .....

"Effectively adding an equivalent level of insulation or airtightness to either a low internal mass or high internal mass structure would be similar to adding identical complexity to two sides of an algebraic equation, they would simply cancel each other out."

... which places the text which you quoted into context. Of course insulation is the paramount consideration in reducing building energy losses, however, insulation & thermal mass are two separate considerations when placing what whasup posted into context.

For simplicity, an analogy ..... take two identical teapots, fill both to the brim with boiling water and let the fabric of the teapots reach equilibrium with the water. What we have is two high mass structures, so we'll empty one pot, leaving one high mass uninsulated structure and one low mass uninsulated structure, both having the same initial temperature - which one cools fastest at room temperature ? ....... now lets repeat the above and immediately place a tea-cozy over each pot in order to provide an identical level of insulation - which one now cools first at room temperature ? ...... I understand that there is a counter argument that it requires more energy to raise the temperature of a high-mass structure to temperature, but comfort levels must also be taken into consideration.

HTH
Z

Cardew

malc_b wrote: »

You misunderstand what the foil's purpose is. Yes radiators work mainly by convection but they are at 70C a or so and only a few cm from the wall so they warm the wall behind them by radiation as well. Heat loss is proportional to the difference between inside and outside. So if all the room, walls, air, etc is a 20C and the outside at 0 then the difference across the walls is 20C. But if the wall behind the radiator is at say 30C then the bit behind the wall is losing heat at 150% of the other parts of the wall. The foil is thus not to reflecting heat into the room or anything like that. It's purpose is to keep the wall behind the radiator cool, at the same temperature as the rest of the room.

It is a a minimal amount of heat lost overall but then foil is cheap. The simplest DIY way to do this is with a bit of cardboard cut into a fat T shape so the top of the T rests on the radiator brackets. Cover that with foil and drop it down behind the radiator.

No there is no misunderstanding on my part.
The question of savings with these foil panels was raised with the Energy Saving Trust in this thread: (only read the first couple of pages)
https://forums.moneysavingexpert.com/discussion/2867980
Essentially the EST stated

Radiator reflector panels do generate a small saving. In a typical 3 bedroom semi detached gas heated home they can
save around £6 and 30kg CO2 a year if professionally installed, whereas DIY installation would save around £3.50 and 18kg CO2 a year. Individually radiator panel reflectors save on average around £1 and 6kg CO2 per radiator as a DIY installation.

We calculate these savings by collating a number of sources. We use the CERT Technical Guidance to derive the average radiator panel saving
from the two different installation types; we then apply average number of
radiators for each house type which is sourced from the Building Research Establishment’s ‘Standard Dwellings for Energy Modelling’ (not publically available).







We then applied our own calculated average prices sourced from Ofgem
data (not publically available) and DEFRA’s GHG Conversion Factors
to get financial and CO2 savings.

However when challenged the EST admitted that they had misread the CERT guidance and that those annual savings(i.e. £6 or £3.50 for a whole house) only applied to houses with solid walls i.e. without cavity walls.

1.78. A reduction in carbon emissions can only be awarded for the installation of radiator panels when they are fitted to external walls.

Furthermore, research by the BRE indicates that an improvement in energy efficiency from an installation of
radiator panels is minimal if the radiator is fitted on a wall with a filled cavity. Therefore, radiator panels should be installed on either solid walls or walls with unfilled cavities.

So EST have conceded that foil behind radiators in a house with insulated cavity walls hardly saves anything - perhaps a few pence per year.

Ben84

zeupater wrote: »

Hi All

I would consider that introduction of insulation should be considered as being a red-herring when considering any property which is not built to lightweight passivhaus specifications. Effectively adding an equivalent level of insulation or airtightness to either a low internal mass or high internal mass structure would be similar to adding identical complexity to two sides of an algebraic equation, they would simply cancel each other out.

High internal thermal mass simply acts as a heat-sink when there is an excess of heat and a radiative source when there is a deficit, therefore providing a temperature smoothing mechanism. I believe that high mass is good and it has suited us well for many years ... we have a property which is comfortably warm in the winter and comfortably cool in the summer .... what more can one ask for.

HTH
Z

High thermal mass does some useful things in a building, but the benefits depend on building usage and the trend is increasingly towards heating or cooling buildings for less time each day than before. The days when many central heating systems in buildings ran 24/7 are fading away with high fuel costs. People want now to turn up at work or come home at the end of the day and have a rapid change in temperature inside on demand as they are unwilling to run the heating when nobody is there. High thermal mass is a hindrance to doing this and results in storing heat that is emitted later when nobody is around to use it.

Cardew

Ben84 wrote: »

High thermal mass does some useful things in a building, but the benefits depend on building usage and the trend is increasingly towards heating or cooling buildings for less time each day than before. The days when many central heating systems in buildings ran 24/7 are fading away with high fuel costs. People want now to turn up at work or come home at the end of the day and have a rapid change in temperature inside on demand as they are unwilling to run the heating when nobody is there. High thermal mass is a hindrance to doing this and results in storing heat that is emitted later when nobody is around to use it.

I take your point, but of course heat is also produced during the day by having large(south facing preferably) windows, and in this respect, high thermal mass is an advantage.

I have a detached annex and during the very cold weather I monitor the temperature, and only switch on the heating when there is a danger of frost damage.

It is really surprising how much the property warms up during the day when the outside temperature is below freezing - several degrees

zeupater

Ben84 wrote: »

High thermal mass does some useful things in a building, but the benefits depend on building usage and the trend is increasingly towards heating or cooling buildings for less time each day than before. The days when many central heating systems in buildings ran 24/7 are fading away with high fuel costs. People want now to turn up at work or come home at the end of the day and have a rapid change in temperature inside on demand as they are unwilling to run the heating when nobody is there. High thermal mass is a hindrance to doing this and results in storing heat that is emitted later when nobody is around to use it.

Hi Ben

Our property was architect designed & specifically built with high integral thermal mass with the intent of maximising solar gain at low sun-angles and slow release storage of energy from solid fuel sources. Despite overnight temperatures around 0C and max temperatures today of ~5C we have only needed to have a late burn again today, so far around 5 hours, and there was absolutely no heating at all used yesterday. The house temperature in the hall this morning was 0.5C lower than yesterday morning.

I have a good friend with a low mass house which was designed & built utilising the very best practices which were around 15years ago (probably very close to current passivhaus standards) where the lack of thermal mass creates a condition where low angle insolation produces overheating at this time of year and we are both aware of the advantages & disadvantages of our respective builds ..... incidentally, the friend in question has recently completed and moved into a high thermal mass property and is leasing out the other one.

High thermal mass is also well suited to low intensity/low temperature heating such as provided by GSHP where the heating cycle which would in normal circumstances be serviced by a 30-40kW gas or oil source is extended to deliver the required heatload over a longer period by a 12-15kW HP unit.

Anyway, enough on thermal mass - I thought that the issue here is the effectiveness of strapping some PC forced ventilation fans to a radiator .....

HTH
Z