Becoming obsessed with insulation

[PaulG626]

Hi everyone,

I have a 1930s chalet bungalow,. Cold drafty house, with issues. Expensive to heat!

Insulation:
1. it has cavity injected insulation.

2. Loft insulation ordinary type 100mm under loft boards and 400mm on none boarded areas, I realise I could put pir under boarded section to improve. I'm considering foil under rafters too to cut down radiant heat - old slate roof no membrane, realise may need vented ridge tiles.

3. I've just finished ground floor putting 100mm pir from crawl space upto floorboards with gaps spray foamed. Intending putting foil type underlay on top of floor boards too under carpets / laminate.

4. I've now started on my bedroom, if has a stud wall (insulated to back), sloping ceilings - no insulation, ceiling (insulated above this with 400mm loft insulation), then down sloping ceiling to almost floor level - none insulated (this area is used as storage behind wardrobes).

I've almost finished insulating all above with 72.5mm insulated plasterboard. See photos.

I'm considering fixing insulated plasterboard to the inside on the external wall ?? As mentioned it has injected cavity wall insulation already, I'm concerned if I don't do it now prior to plastering I'll regret it or could regret if I find it causes damp issues?? If I was to do it what thickness??

I'm going to have a new upvc double glazed window with trickle vent in.

Another thought is to put foil type insulation on top of floorboards - under carpets / laminate, would this cause a problem as it 1st floor stoping heat rising from ground floor, ect????

5. I'm becoming obsessed with it, just had conservatory rebuilt with new windows and solid roof. The front double doors were old leaded glass which are now getting encapsulated into double glazed units. Even considering getting a thermal camera ie flir 1 to identify problems.

6. Please help me figure it all out, I guess the main question is should I add pir insulated plasterboard.to inside of external walls that have previously had cavity wall insulation injected to it???

Kind regards Paul

 

[securespark]

In my experience, injected cavity insulation is a PITA. It can cause transfer of damp and there can be patches where the insulation has not reached.

 

[PaulG626]

 

[PaulG626]

The cavity wall insulation was done years ago and has caused no problems.

 

[robinbanks]

I'm considering foil under rafters too to cut down radiant heat - old slate roof no membrane, realise may need vented ridge tiles.

Fruitless exercise, I'd say

find it causes damp issues

Insulation doesn't cause damp; generating moisture that you don't get rid of causes damp. Insulation reduces risk of condensation by making surfaces warmer, but it doesn't mean you can just carry on loading the in-house air with moisture. Generate less moisture (pans with lids, extract fan to outside, don't dry washing on radiators, ensure the tumble dryer exhausts to outside or is condensing, ensure ventilation when showering) and ventilate adequately for the moisture generated. Consider fitting a heat recovering ventilation system

Another thought is to put foil type insulation on top of floorboards - under carpets / laminate

Directly under it? It'd get ruined by walking on it, especially if anyone wears heels. do it under the ground floor boards only

should I add pir insulated plasterboard.to inside of external walls

It's law of diminishing returns but I'd say a generally useful upgrade; you didn't say how big the cavity is, but 100mm of wool or bead insulation is vastly better than nothing but only worth about 50 ish mm of PIR (what you get on the back of plasterboard)

Look to resolve draughts too; no point putting insulation everywhere if you let cold air blow past it. Your Flor can come in handy for that; on a cold day, with the heating on if you can arrange for a high volume extract of the house air you'll find where the cold air gets sucked in

 

[PaulG626]

The maim question is should I also put insulated plasterboard on the inside of the external wall, if so what thickness, the cavity is 100mm with injected wool type.

I realise the generated moisture is an issue so considering new windows with trickle vents / using dehumidifier too.

Draughts much improved by recent under floorboards ground floor insulation. The under carpet foil im thinking of is more of an underlay with foil backing.

 

[robinbanks]

if so what thickness

What's your target u value for the walls? Passivhaus (houses that do not require heating systems) are between 0.1 and 0.15 with minimal thermal bridging, but it's a whole-house approach rather than something you do "here but not there" and upgrading an old house to passiv is an incredible undertaking..

The under carpet foil im thinking of is more of an underlay with foil backing.

Ah, I thought you were considering carpeting on top of 50mm of celotex

 

[PaulG626]

Not really sure about target u values, guess I just want to improve the house one room at time, the sloping ceilings have no insulation at all so will do those in future.

There's other issues too like bay windows no insulation above, front dormer suspect none to roof, front door 1930s type with recessed door into 4 foot into hall suspect no insulation above.

 

[PaulG626]

Obviously time and costs are an issue, its a diy approach, working on the principal of anything better than nothing. I've looked at u values but find them confusing

 

[PaulG626]

Ie not sure about u value of the cavity wall wool type injected insulation, its brick built external and internally with 100mm cavity, plastered to inside and cement rendered to outside (intending having k rendered in the future).

Aware could change dew point so need advice on applying internal insulated plasterboard to the inside, what type of pir ect, what thickness????

 

[PaulG626]

Would a kers vent help?

 

[JP_]

I put 50mm PIR on internal walls of my 1930s bungalow, no cavity wall. I don't know about U values, but it has massively improved the warmth and comfort. We never have the heating on at night, even when minus 5 outside. Floors were also insulated, and plenty stacked in the loft too.

 

[cdbe]

My house had wool injected 10 years ago, I've been replacing the roof and have found it has settled by about 4-500mm at the top of the wall - I would recommend checking and topping up if necessary/accessable.

 

[robinbanks]

have no insulation at all

They'd be the areas to prioritise

I've looked at u values but find them confusing

Here's the short, short version: the lower they are, the lower your heating bill for maintaining your house at some given temperature

--

U values describe how much heat is lost through an area of house envelope between the warm bit (inside) and the cold bit (outside)
U values are expressed as watts, per m2 area of wall/roof/floor, per degree of temperature difference

If your wall (and ceiling and floor) was 0.8w/m2/K, and
it was 20 degrees in side your house, and
it was 0 degrees outside, and
your walls (and ceiling and floor) were 64 sqm (sounds a lot but that is a 4m x 4m room that is 2m high, i.e. a house the size of a small living room)

Then the heat loss through the walls is 0.8 x 20 x 64 = 1024 W

To maintain your 4m x 4m x 2m house at 20 degrees when it's 0 degrees outside, will require a 1kw fan heater on constantly. it pours 1kw into the room and that 1kw soaks out through the walls and is gone, constantly

In electrical terms to run that fan heater is 30p per kilowatt of power (it's 1 kilowatt) per hour.. so effectively it costs you 30p an hour, or about 2600 quid a year to keep that small house at 20 degrees.

Of course, there are many factors; the temp outside changes, it rises, it means less heat soaks out of the walls. You add insulation, lowering the U (if you get the walls down to 0.2 U you only have to have the fan heater on 256 watts, a quarter of the time, a quarter of the cost. We don't heat constantly etc but the main thing with the U values is to set a target that youre happy with and insulate to meet it. In a passivhaus that really might mean you look at the size of your windows, and the wattage of your washing machine and fridge and how often these things run, and do that for every day of the year, and work out the total amount of wate heat in the house, and then how much you need to insulate to do away with the heating system..

..but in a normal house you might be more like "what can i sacrifice in terms of wall thickness, and how much do I want to spend on insulation etc" - you might only have a 100mm gap and you really want to get to 0.2 U so you're putting 100mm of kingspan in there. You might be aiming for 0.15 and have loads of space so 300mm of wool it is, and it's the same price as kingspan

If you get the walls U low enough that the waste heat from all your household appliances, your body, and things like sunlight streaming in through the window, covers the heat loss then you don't need to run the heating - that's a passivhaus but they're designed to the finest deail and constructed with a percision like nothing else. It's huge work to get a 1930s anything to that, so most people settle for leaps and bounds improvements that come with some reasonable amount of insulation and careful detailing. I'd use 100mm PIR

Aware could change dew point

Yes, but favourably; it's easier to keep the house warmer, with less fuel. In general, strive to keep internal surfaces above 13 degrees, and also strive to minimise the amount of moisture you load into the air

Would a kers vent help?

Yers assuming youre talking about the heat pump but the thing that these kind of products never mention is that the heat has to come from somewhere..

"Oh it comes from warm stale air in the bathrooms" - yes, but how did it get warm in the first place? You paid to heat it! If you have surplus waste heat then sure, run one, and cool the house down with the output from the heat pump because you have too much heat and want to get rid of some by stashing it in hot water that you'll enjoy using. That makes sense..

..but when you're running a heating system to warm the house up, and you have a heat pump perched on top of the cylinder taking heat from the house and putting it into the water you are going to have to replace that heat if you want a house that is the temperature you want. Yes, it's bonkers to just take that warm air and throw it out into the world via a bathroom extract fan or open window (or even pull the bath plug and let all the warm water down the drain - let the bath go cold first so it gives up its heat to the house); that's an outright loss of money paid to heat that air that could be used to heat water - but you don't get it for free, unless it's true waste (and it seldom is)