wall insulation -length before feel affects

waster81

Hi looking at getting walls insulated in my bungalow. Some of the back walls are freezing to touch them.

Wondering how long after we get the walls insulated with the beads, should we feel an affect on the warmth of the rooms.

Would it be the next day, week months?

Victor

Almost immediately, assuming there aren't any complications.

Poor Uncle Tom

As Victor said, straight away.

waster81

Thanks for that.

Neighbour up the road got there's done couple of days ago, their walls are still cold.

Does that mean there are issues or is it just a matter of waiting.

justflow1983

When and where was the insulation added? Also, it would depend on the heating system.

Insulation acts as a barrier to heat transfer, because it doesn't absorb or transmit heat well. It doesn't stop this transfer, but it slows it down significantly. Materials like blockwork & concrete are the opposite, they absorb heat very well so it moves through the material and then out the other side. This is called having a high degree of thermal mass. Think of heat transfer as two ponds with a channel in between them, when one pond is more full, it goes into the other one until the water levels out, your heat transfer is the water going from an area of high heat (interior) to low heat (exterior) and the insulation makes the channel smaller. Every area that's poorly insulated makes that channel larger.

If your masonry is inside of the insulation, you are going to have to "saturate" that masonry with heat with your heating system before the space actually feels warm. This extra time is called "thermal lag." If the heating system can't put heat into the walls faster than it escapes through the insulation, then they will continue to feel cold. In fact, masonry will probably always feel slightly cold because it wicks the heat out of your hand if you touch it.

They may need to upgrade their heating system as part of their overall thermal upgrade. Or it just may be that there is such a large amount of stone or concrete between the inside and the insulation that they're still waiting for the concrete to "fill" with heat... if its more than 200mm thick it could take a while to stabilize.

All of that said.... it should not be any more than a matter of hours unless they insulated wrong or missed some large areas like the roof or around windows or something else like their heating system not working properly.

waster81

Cheers for the explanation. Not sure what system they have.

We have an oil burner with radiators in each room, when you say upgrade the system do you mean replace the burner?

justflow1983

To be honest, I don't know enough about heating to answer that question. I would find out what the U-Value of your walls & windows would be after getting the insulation. A heating provider or an M&E engineer should be able to size a system based on the rate of heat loss from your building envelope, relative to the size of the house. It's probably not an issue, if your current system keeps the house warm without the insulation, then its probably bigger than you'd need once you aren't losing heat.

If you do get your house insulated, also have your airtightness done at the same time. It will make a huge difference.

sydthebeat

justflow1983 wrote: »

1. ......... because it doesn't absorb or transmit heat well. .........


2. If your masonry is inside of the insulation, you are going to have to "saturate" that masonry with heat with your heating system before the space actually feels warm. This extra time is called "thermal lag."

1. one factor to remember when choosing insulation is that some insulations DO absorb heat better than others. Generally dense insulation material such as rockwool, sheeps wool etc ie the 'quilted' insulations are much better at absorbing heat than the poly type product such as polystyrene, PU and PIR ie the 'board' insulations.

2. this ability to absorb and store heat is referred to as thermal inertia or decrement delay. Constructions, and insulations, such as described above as quilted, can store heat and allow it to dissipate back into the dwellling when heating periods are off. Therefore, to continue the analogy of the ponds above, the 'saturated' wall will still allow heat back into the dwelling even when the pond is dry. This is why thermal mass is a factor when choosing insulation.

Timber frame constructions with low thermal mass, and which use 'board' type low density insulation may have a short 'thermal lag' and be very responsive to heating alterations, but also cool down quicker in times off no heating, whereas high thermal mass dwellings will not cool down as quickly.

obviousluy this rate of heating up / cooling down is much more influenced by the amount and detailing of teh insulation and construction elements.

justflow1983

sydthebeat wrote: »

1. one factor to remember when choosing insulation is that some insulations DO absorb heat better than others. Generally dense insulation material such as rockwool, sheeps wool etc ie the 'quilted' insulations are much better at absorbing heat than the poly type product such as polystyrene, PU and PIR ie the 'board' insulations.

2. this ability to absorb and store heat is referred to as thermal inertia or decrement delay. Constructions, and insulations, such as described above as quilted, can store heat and allow it to dissipate back into the dwellling when heating periods are off. Therefore, to continue the analogy of the ponds above, the 'saturated' wall will still allow heat back into the dwelling even when the pond is dry. This is why thermal mass is a factor when choosing insulation.

Timber frame constructions with low thermal mass, and which use 'board' type low density insulation may have a short 'thermal lag' and be very responsive to heating alterations, but also cool down quicker in times off no heating, whereas high thermal mass dwellings will not cool down as quickly.

obviousluy this rate of heating up / cooling down is much more influenced by the amount and detailing of teh insulation and construction elements.

Are you saying that batt style insulation has a thermal mass? Because there isn't any other way to "absorb" heat, unless you just mean that the heat to the inside isn't going any further because of its low conductivity. I've always worked on TF buildings that used batt insulation in the studs with/without a rigid board to the outside, never with board only. Never really thought about it actually other than its the way I've always done it.

My thermal mass/thermal lag explanation was definitely a little simplistic, but the principle was there. The saturated thermal mass re-radiating into the room is just the same pond analogy at a smaller scale.

If we're talking about retrofitting an existing dwelling such as the OP's, the thermal mass of the construction is essentially fixed, so you're just choosing how to block the heat transfer and where within the wall buildup you'd like to locate that block (which is your only way to control thermal mass and thus lag within the envelope). There is also the further concern of bringing the dewpoint as far out as possible to eliminate interstitial condensation, which is why in this sort of case I would prefer a rigid board to the outside of a masonry layer, in order to put the dew point within the rigid, low moisture board.

sydthebeat

justflow1983 wrote: »

Are you saying that batt style insulation has a thermal mass? .

yes, of course.

every material has a specific heat capacity, it just depends on what value it has.

im not referring to the ops case in point, just saying that 'thermal lag' is not necessarily a bad thing, as it occurs at both ends of teh heating period.... ie slow to heat up, slow to cool down....

one of the most prominent tf companies in the country at the moment simply use PU board between studs.