Your generating a lot of moisture just being there, let alone with what you’re doing, and whilst traditional walls may be ‘breathable’ that’s a relative term. They don’t transfer moisture all that rapidly, and your walsl are certainly less permeable than the breathable insulation you may’ve gone and lined them with.

So with no vapour control moisture will pass happily through that insulation and come to a ‘relatively impermeable’ surface that’s also rather cold.

That’s a recipe for disaster.

With a traditional solid wall that’s not a huge problem. There will be times of the year that you may get interstitial condensation in the fabric of the building but as long as that’s minimal it’s not necessarily damaging. Moisture can still migrate to the outside, partially helped by the heating from the inside. Also, over the course of the season, saturation from the outside will dry out, again partly helped by that internal heating. Some moisture may also evaporate back inot the house, but this isn’t so significant.

If you come along and insulate that wall, you will inevitably make it colder thatn it would otherwise be, and if you use a ‘breathable’ construction, allowing moisture to penetrate through to the now colder wall unhindered, you run a considerble rick of severe, potentially catastrophic, interstitial condensation.

I agree entirely with Seanie’s comments (13 January). The issue of interstitial condensation has been well established over a number of years and calculations are recommended to calculate the location of the dew point (the point at which condensation is likely to occur in the construction). This is set out in BS 5250: 2002 – Code of practice for control of condensation in buildings. It is not simply something that the manufacturers have created to sell more product. Manufacturers do however give details of how their own products can be best used to meet the recommendations of the Standard, which should not be ignored. And no, I don’t work for a manufacturer in case you wondered !

People have tried a variety of ways to try and address this, but most haven’t been tested over time. There isn’t really a strategy for internal insulation that you could confidently say will work, short of gutting the property and rebuilding a shell within a retained facade. That’s not to say it can’t work, just that it’s a very tricky area and should be approached with some caution.

I agree with you regarding miracle products but I don’t understand how internal insulation could damage the fabric of the building. I would have thought that it was less likely to harm a building than insulating from the outside and accidentally preventing it from breathing.

It is true that insulating the outside has the advantage that the mass of brick or concrete forming the structure within this envelope would act as a thermal store. This prevents you loosing all the heat from a room every time you open the door if the air is the only store of heat. However ideal this might be I think it would be impractical on a retro fit and is best for new build properties. The cost of tiling and cladding the outside would be prohibitive. Many older buildings are wood panelled from floor to ceiling and those pannelled up to waist height were usually an accepted way to keep the rising damp (prior to damp proof courses) from the bottom of the walls, from cooling the room. Four Poster beds and the box beds found in vernacular buildings were one way of creating a small space within a cold building that could be kept warm with hot water bottles etc.

Building a shed within a large room would be an extreme form of internal insulation with a huge air gap.

I’d also avoid Sempatap. With a thermal conductivity no better than mineral wool, and at 10mm thick, it’s effect will be pretty minimal.

Internal insulation has potential problems. With a cavity wall it might be easier to prevent, but with solid walls there’s a real risk you could seriously damage the fabric of a building. With careful detailing it might be OK, but that’s easier said than done.

http://theyellowhouse.org.uk/

You are right in that new technologies are happening all around us but sometimes the better product fails because there was more money behind the successful market leader. It sold only because they had superior advertising and marketing, not necessarily a better product. Personal recommendation and unbiased advice (if you can find it) are the best sales tools.

Your last paragraph is the best for the DIYer. I always try to make/do only things that can be reversed so I don’t get put of improving on my last mistake because of all the energy put into it. Screws may cost a bit more than nails and take longer to use but are much easier to disassemble if necessary.

Finally your last recommendation about blankets/carpets/tapestries is excellent. Some of those old castles weren’t always cold and draughty when they would line the walls with tapestries. They weren’t just decoration, they were insulation!

On a slightly different subject, isn’t the Transition movement all about surviving after peak oil and reducing our dependence on it. If we are true to that ethos, surely we should not be endorsing insulation products that are oil based?

New developments in building technology are happening all around us,and some will be superceded/discarded before fully trialled, as better ones come along.
Tempting to suggest ‘sticking plaster’ approach till the upheaval settles and a consensus amongst professionals emerges about best practice. But will it settle?
We’ve just renovated our house (and gained experience of triso super 10, mineral wool,celotex/kingspan, sempatap, hempbatts).All have limitations: I suspect a multifoil, high performance, breathable insulation is about to make most of them redundant.
Hidden moisture can cost more, financially and in terms of carbon emissions, than draughts and cold-bridges.
So, my advice would be, get a professional and get a guarantee that means some thing, or do it yourself in a way that can be taken apart again easily, and cheaply (Old woollen blankets/carpets/tapestries on the walls for the winter)

Thermilate – I have requested technical details from Thermilate as they are not readily available on the website. However looking at the testimonials is revealing as it shows the low number of referrals, duplicate names and non-scientific comments to ‘prove’ their efficacy (eg. “The investigator was amazed that the paint was reflecting the warm heat immediately away from the roof, once it had dried on the surface. This was easily noticeable by simply touching the surface.” or “To our excitement, the temperature in the room is now 4 degrees higher”). DEFRA’s report ‘Environmentally Beneficial Nanotechnologies’ says ‘This product does not make use of nanotechnology, but of micro technology, and independent verification of its claims has not been obtained.’
Thermilcoat – The technical test downloadable from was a simple basement room heated ‘before & after’ with no windows, undertaken by the University for Architecture, Construction and Geodesy in Sofia. Despite claims that the material was developed by NASA there is no real technical explanation of how it works or what its make-up is.
Nansulate – has a cure time of 30-60 days. It incorporates a nanocomposite called Hydro-NM-Oxide, a product of nanotechnology. From the H&S report “Nansulate Coating is a water based product consisting of less than 10% dipropylene glycol monobutyl ether, a proprietary styrene-acrylic copolymer, several commercial surfactants and amorphous silica.” and “Avoid eye contact and prolonged or repeated skin contact with the product. Provide good general ventilation is use areas by opening windows and doors. Avoid breathing dust that may be generated during dry sanding, etc. of surfaces treated with the coating.”

Defra also says ‘…. such applications are relatively niche and these products do not appear to be replacements for mass insulation. The cost of such applications will remain prohibitive until the environmental implications are assessed. There is also a range of water based coatings; the Nansulate range of products from Nanotech Ltd which are designed to be applied to residential buildings on walls, metallic and wood surfaces and exterior walls and claim to significantly reduce heat transfer. Such a range of products may begin to address the market gap of insulation appropriate for solid wall buildings, but there is little independent verification of the efficiency of these products so far…….. A technical challenge remains in the aesthetic insulation of solid walls, but claims of the potential of nanotechnologies in this area are tenuous….. There is much work remaining before solutions at the nano‐level represent a way forward for insulation.

Architects generally would suggest you use materials recommended by the British Board of Agrément. An Agrément Certificate is awarded to a product only after it has successfully passed a comprehensive assessment involving laboratory testing, on-site evaluations and inspections of production. These tests are done in identical test situations so that products can be readily compared and you can search for all approved products on their site.

There can be no substitute for a site visit, careful consideration of the existing building & its needs, assessing the available budget & the practicalities associated with any potential option. I would suggest you find a reputable architect or building surveyor & think about a ‘whole-house’ retrofit plan. I will attach some relevant links in an additional post, I find that posts appear out of sync as your moderation hangs on to some of them!

Developing a refurbishment strategy – http://www.greenspec.co.uk/html/refurb/strategy.html
Embodied energy – http://www.recovery-insulation.co.uk/insulation_comparison.html
Insulation comparisons & Life Cycle Assessment – http://www.greenspec.co.uk/html/materials/insulation.html
Kingspan on embodied energy – http://www.kingspanpanels.com/Resource_Centre/Technical-Information/Sustainable-Construction/Sustainable-Insulation.aspx
BBA certificates search – http://www.bbacerts.co.uk/certificate_search_results.aspx?SearchType=Product&KeywordSearch=insulation

While at college I remember a visit to the Building centre where there was an exhibit showing the relative thermal characteristice of common materials. I was amazed to fgind the plain old wall paper was equivalent to several inches of some insulation materials. I would never try and use anything that just treats the effects of condensation. If you find the source of the moisture, a double layer of wallpaper is pretty good insulation. If it starts to come off the damp problem still exists.