Thermal Imaging Survey

[DonL]

I recently got involved as a volunteer in carrying out some domestic thermal imaging surveys of houses from the inside.

The guy who developed the system has been able to get some grant funding to support initial surveys and I've found them really informative.

His method is to have the house heated for 48hours before the survey (during cold weather - he looks for at least 10C difference inside to outside) and then we come along and install a large fan in one of the door openings to suck air out of the house and depressurise it by about 50Pa.

He then goes round the house with the thermal imaging camera and the householder holding a remote display of the camera view. Temperature can be measured using crosswires on the image and the whole survey, with sound, is recorded and given to the householder at the end.

There is a short debrief at the end of each visit to discuss results and recommendations.

I was amazed at the draughts we found in my house and also showed up areas where the loft and wall insulation were imperfect as well as poor thermal performance of window frames.

He has found many surprising results: one was a converted barn where high performance internal insulation boards had been stuck onto the walls with dabs of grab adhesive. The draughts came down the back of the boards and out under the skirting - you could see the dabs as warmer spots in the image!

I've helped with 14 houses so far (each takes about two hours) and I'm sure the householders have soon been out buying draught excluders, sealant, insulation etc. One chap was on the phone the following morning trying to arrange cavity wall insulation!

Perhaps another way of encouraging people to upgrade the thermal performance of their houses, save money and decrease CO2 emissions? 

Don

[dimogga]

Heated for 48 hours? AT what temperature or do you just mean heating on at some point?

[bath_ed]

Very interesting. I have been wondering for a while whether it would be practicable to actually measure the insulation properties of a house as to my mind anecdotal evidence is of little value: you can say, look at your gas bill and think it is high or low compared with another house, but how do you know whether it  is just because you have the heating on more or less?

The scoring system in the energy certificate is very unscientific too in my opinion as it just puts assigns walls, roofs etc to broad categories. In my case the surveyor did not even know what the cavity insulation was and assumed there was none.

I'm a little uncertain of sucking the air out of a house as surely all houses need to 'breath' to some extent. This method seems to detect heat loss by mass movement ie draughts, but maybe it would be more useful to determine heat loss by conduction?

[clivejo]

I my opinion thermal studies should be completed before any further energy saving projects are undertaken.  I dont see the point in spending thousand of pounds at tackling the wrong problem!  One scenario I heard recently was a home owner who got new tipple glazed windows in, but was still plagued with cold and damp around the windows.  The window company where baffled and blamed the loft insulation and the home owner for not heating the house properly, but there was plenty of insulation down and the heat was on.  In the end a thermal camera was hired and the problem was that when the window-fitters installed the windows, they had removed the little polystyrene beads in the cavity all around the windows!!  

I have been trying to get the same for my own house as I believe that the fibreglass used in my cavities has fell down and there is a 3-4ft gap along the top with no insulation!!

[dinitro]

Hi

I bought a thermal camera for this reason and found not only thermal leakage problems but also damp.

I have solid walls and the loft conversion has a cold roof.
The thermal camera has already found areas where the insulation has moved.  I am now thinking of lining the whole of the interior of the conversion that was done in '84 with k17 kingspan.

The camera also correctly identified the location of pipe runs in the ceiling void.

dinitro

[clivejo]

Hi

I bought a thermal camera for this reason and found not only thermal leakage problems but also damp.

I have solid walls and the loft conversion has a cold roof.
The thermal camera has already found areas where the insulation has moved.  I am now thinking of lining the whole of the interior of the conversion that was done in '84 with k17 kingspan.

The camera also correctly identified the location of pipe runs in the ceiling void.

dinitro

How much was the camera?  Im wondering if a community group could purchase one and do free home surveys for local residents.  I think it would be a great investment.

[Richard Owen]

How much was the camera?  Im wondering if a community group could purchase one and do free home surveys for local residents.  I think it would be a great investment.

I'd be interested too.

[DonL]

I'm a little uncertain of sucking the air out of a house as surely all houses need to 'breath' to some extent. This method seems to detect heat loss by mass movement ie draughts, but maybe it would be more useful to determine heat loss by conduction?

The survey addresses conduction by showing the cooler surfaces in the normal way a thermal imaging camera does detecting areas of poor insulation and indeed showing the joists in the loft and the higher conductivity cement between the insulating blocks in the wall behind the plaster.

Houses may need to breathe to some extent but we find in most of the housing stock around here (including embarrassingly my own) is not breathing but huge draughts!

Referring to the point about heating the house; the intention is to get some approach to steady state through the fabric so that areas of poor insulation can be seen by the lower temperature on the inner face. The rule of thumb seems to be to heat the whole house to an ordinary kind of temperature for 24 hours if cavity wall, and 48 hours if solid wall, before the survey. Obviously it needs to be cold outside and we aim for a temperature difference of at least 10C.

Don

[Paul and Rona]

Hi All,
        Thought you might like this link...

http://www.hoagieshouse.com/IR/

It details a DIY thermal imaging using cheap webcams,

Seems like the Mod is quite simple, remove the IR filter and refit a Visible light filter.

Not quite in the Multi thousand thermal imaging systems league but, looks like it may be usefull.

Regards Paul.....

Think i feel a project coming on .................

UPDATE, I think "optical" IR and "heat" IR are at quite different IR wavelengths, not sure how good or bad a ccd sensor would function at "heat" wavelengths ??

[Ivan]

I've got a thermal imaging camera, and long term members will probably remember me offering thermal surveys on the forum in past years. I've done thermal imaging for 4 or 5 seasons now (including Buckingham Palace a few years ago!).

The 'cheap IR' modification isn't useful for thermal emission work. Paul you're absolutely right, thermal emissions are much longer wavelength than the short length IR that CCDs are sensitive to. The CCD webcam will be totally blind to thermal emissions with or without the modification. You don't even need the filter to see short wavelength IR. The filter is just to cut out the visible light. Take a standard camera phone, digital camera or whatever, and look at the diode on the front of a TV remote control whilst pressing a button - you'll see it flashing clearly, in the short-wavelength IR.  If you follow the website instructions and make an IR webcam, try pointing it at a house in the dark, you'll see nothing, as the thermal emission wavelength is much too long for the CCD. In fact, they don't pass through the glass/plastic lens itself, so it's unable to focus a long wavelength IR image even if it was sensitive to it (you need a germanium lens).

I've found that you need a minimum of 14C temperature difference to capture the finer thermal detail. If you want to see problems in cavity wall insulation, you'll ideally want in excess of 20C difference.

There are a few problems you'll encounter with thermal imaging:

1)windows reflect. If you are looking up at a window, you'll see a reflection of the sky. If it's cloudy, you'll see the cloud emissions reflected in the window. If it's clear, you'll see the cold of deep space reflected in the window. The angle you view windows at is very important.

2)Damp and heat-loss are pretty difficult to differentiate without actually using a damp meter (or your hand to feel for damp)

3)Emissions are dependent on the emissivity of what you're looking at. For example, white walls might emit less than dark walls, but if they are warm they will conduct heat to the air regardless of their IR emission, especially when it is windy.

4) IR imaging is very much a relative tool. You can tell if the object is warmer or cooler than another object you are viewing. Absolute measurements are pretty difficult. The cross-hairs with the temperature reading need to be calibrated for the material being observed. So concrete will require a different calibration to brick and different to glass or slate. So even if the house surface is absolutely uniform in temperature, you will read different temperatures on different parts of the house due to the different materials

5)IR imaging DOESN'T see heat emission from warm air leaking out of a house. However, you will see the warming effect on nearby materials ie surrounding the area where the air leak is, and in the case of condensing steam, you'll see the heat emitted by particles of water when the steam starts to condense.

[andrewindevon]

I've been looking for someone to do this in North Devon, I've had some quotes around the £500 mark.  I know the camera's aren't cheap but it's just too much 

[clivejo]

at £500 a pop would be a nice wee earner!

[Heinz]

Judging by the Ebay prices it would only take a very few £500 surveys to be in profit....

H

[Ivan]

I've charged £100 a survey and that included the mileage cost, as long as I can get a few people together in a similar area, so I can do a few on the same night. That includes the time and fuel driving, between 1/2 and 1 hour on site and 1-2 hours processing the images afterwards. I've not got anywhere near recovering the cost of the camera I purchased, but it's a way of justifying an expensive toy!

Maybe I should be charging £500?!

[andrewindevon]

Ivan, fancy a trip to North Devon?  I can offer beautiful scenery, lunch/dinner/pub and a spot of thermography?  My wife bakes a mean cake as well