damp
Hi Robert !
Rising damp is identified by drilling a hole into the suspected wall at the bottom of it and one at the top .
Than you analyse the dust from each for moisture content . The dry dust would easily "dust" while the damp dust would be somewhat clogging together .Signs of mould , wallpapers condition etc. .A bit of experience would be handy , try it out on a wall where you are sure about it's condition . Otherwise you can get a damp meter from the tool hire shop or buy one yourself , which might be an option for a larger project .
A thermal bridge is the weakest point - in insulation terms - of a structure where you get a temperature difference of 6 or more degrees Celsius which in turn causes condensation .In your car it would be the window for example . In a standard building this could be the window pane , its frame , the entrance door , the lintels and ducts leading to the outside . In buildings that had been insulated from the inside ( a typical DIY mistake , but it's tempting not to use a scaffolding and working inside is so much more comfortable ) these thermal bridges would be found at floor levels and in corners that are created by partition walls. Usually the ground floor inside is a bit higher than the soil level outside . So when you insulate the inside wall the cold could creep under the floor causing musty smells , rotten carpet edges and skirting boards .
Same goes with ceilings -where there is no insulation there will be condensation .
" O " used a plastic sheet between the original wall and the newly installed inner insulation .I wouldn't go for that solution . Either the wall is dry or not . Blocking moisture in it makes the worst of it ,the wetter it is the less it insulates.It is the air trapped in the wall that insulates,not the water,and the longer it has time to build up the fewer air it will leave . Future problems ( asthma due to fungi spores growing happily behind it on the damp wall -they will find their way even through gas mask filters ! ) would be " build-in " .
Tackle the problem is my advice - don't cover it up .
Insulation is an issue where a lot can be done wrong , the sick- building-syndrome is what the occupier will experience . Structural damage can be caused as well ( rotting timber , concrete weakening by saltpeter excreting moulds and faulty electrics are only a few )
Don't safe on the penny when it can cost your health .
The most important thing is to work logical .
I stop here before it get's out of hand .Good luck !