# Cavity Wall Insulation..how long?



## Badgolfer (29 Jan 2011)

A query on cavity wall bead insulation...is there a lead time before this insulation becomes effective? 

I have just spent a fortune filling the cavities in my house walls this week. So far the temperature loss overnight in the house is the same as it was prior to the work being done. So it is not working. Anybody know why?


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## onq (29 Jan 2011)

Thermal Performance:

Several factors will influence the ability of your house to retain heat and these fall into the following broad categories.

The Site:


 The location (geographically, macro-climate, prevailing winds)
 The exposure (solar profile, micro-climate, screening effects, overshadowing)
 The elevation (height above sea level)
  The History:


 The age of the building (weathering, condition, settlement, repair)
  The time it was built (the then-current building practices and regulations)
  The Design


Shape of the house, number of stories, projecting bays or dormers, colour and materials
The orientation (position on site, rotation, available sunlight, positions of windows)
 The sealing of the envelope (water and wind penetration and pressure changes)
 The design (size and location of windows, ratio of vs wall, avilable thermal masses and airlocks, quality of components - windows doors, etc)
 The component design (compatibility of materials, rates of expansion, thermal transmittance, installation, sealing and making good)
  The Technology


 Heating (Older Tech - Space Heating - Central Heat Source with Chimney + central heating + unsealed building)
 Heating (Newer Tech - Fabric Heating/Distributed Heating with no Chimney + Mechanical Ventilation and Heat Reclamation + highly sealed building)
 Fossil Fuel Sources of Energy (not affected by season or climate
 Sustainable Sources of Energy (affected by seasonal and climatic variations)
 Integral Insulation (part of the design - either integral to the construction method or incorporated during site-work)
 Retro-Fit Insulation (installed after completion in the presence of unknowns)
 
All of that may look complex, but its just a brief overview of the facts that can affect your house feeling warm.

Now on to some specifics.


 A house in an exposed site may benefit as much from sealing the construction as insulation.
 Older houses in particular can have huge infiltration loses through ill-fitting windows and doors.
 Houses with a open fireplace, no porch and direct rear access suffer hugh air-chage rates.
 A house with large, north-facing windows may not benefit as much from insulating walls.
 Its colder this week where I live with a significant amount of wind earlier in the week.
 Beads can be a hit and miss affair unless the operator is skilled and leaves no "gaps".
 Beads are in-cavity as opposed to warmboard (in-room) and will warm up slower.
Cavity beads might be on your list after attic insulation and improved windows.
 Before you did anything to your house you should have sought advice from a building energy rating specialist.
They will assess your premises, evaluate the several factors (many of which I have noted above) and suggest improvements.
They  can confirm which are the most effective, the most cost-effective, and the easiest options to install.
They will tell you your houses  existing thermal performance as well as the theoretical improvements you can expect, depending on workmanship and sealing.

The gist of this is that people who rely solely on salesmen selling them  a single product are not getting an overall picture of their house.
An older house with a large north facing picture window,, no porch, and open fireplace and direct rear access [not through a utility room, for example] may not notice much of adifference after installing cavity beads.

ONQ.

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## Badgolfer (29 Jan 2011)

Thanks for your very valuable input ONQ. 

It is a two story, five bedroom house which was built in 1980, I have new triple glazed windows, the attic is insulated to a depth of 300mm and there is no evidence of draughts through the rooms. 

I have been monitoring temperature on the following morning after normal room heating of the night before. So far the temperature reduction has shown no improvement since cavity wall bead insulation installation of three days ago!

Rgds BG


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## wbbs (29 Jan 2011)

Total amateur here but surely the aim is to reduce running costs of heat not whether or not the house is still warm in the morning?   My house is always freezing in morning no matter how warm it was night before and if I am intending getting it looked at with a view to improving the insulation but my aim would be to have to use a lower setting on the boiler to bring and keep the house to the temperature I like it during the day and evening.   I can't imagine any amount of insulation would hold the heat overnight in this sort of weather without the heating actually being on.  I am sure onq will be able to put better what I am trying to say and maybe I am totally wrong and looking at it the wrong way altogether.  

Would like some advice too before I go ahead and pay money to anyone, I already have sheets of aeroboard stuff in cavity (built 1980) and I thought that filled the cavity but a friend of mine who has a house only 5 or 6 yrs old got cavities pumped with beads even though there was already some sort of insulation in the cavities, how does this work?


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## Sandals (29 Jan 2011)

I know we insulated attic last year from having none at edges and a few bits down the middle runway under the truss roof (was easy to lay insulation) and the effect was instant.

Looked into getting cavity bead but have held off on it so far, people we'v talked to who have it done noticed the house held the heat better but they did think they needed the same heat/energy usage to keep house warm.


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## Badgolfer (29 Jan 2011)

WBBS - The reason I check morning temperature is because the difference between the temperatures of say the sitting-room at the end of the evening and the following morning indicates how much heat has been lost overnight through the ceiling, walls and floors of that room. 

Therefore as you improve the insulation of that room the delta in temperature between evening and following morning should be lessened - always taking account of the outside temperature.

I have been advised that the effectiveness of the bead insulation improves after four days or so....we will see!!

In addition I can measure boiler oil usage daily to confirm or otherwise if this stuff works!!


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## wbbs (29 Jan 2011)

Right, I follow what you mean now.  I wonder though when during the night does the last of the heat go, I know I fell asleep few nights ago while watching telly on my comfy couch, woke up about 4 a.m. and noticed that the house was still quite warm, of course after my little nap I could not get back to sleep and by 6 a.m. when I was still awake the place had become freezing.   So I wonder whether for example your house had lost its heat by 3 a.m. before the beads is it now keeping it till say 7 a.m.   

Keep us posted on what you discover before I shell out wads of cash too.  Thanks


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## Badgolfer (2 Feb 2011)

OK we have a solution and clarity.

Apparently what happens is that the inner wall takes some time, subsequent to cavity filling, to absorb heat from the room i.e to warm up....in my case it took about five days.

After filling the cavity far less heat is absorbed by the wall and as a result this heat will go into the room to warm the people and the cat.

In my sitting room, prior to cavity filling, the room radiator was not capable of bringing the room temperature to above 19C - even with the radiator kicking out as much heat as it was capable of all evening.

Now, subsequent to filling the cavity the room temperature reached 20C in just a couple of hours. Therefore much less boiler running time!! I have graphed the two situation but don't know how to stitch a graph in here!

In addition the room is much warmer the following morning. So my initial skepticism has evaporated...and I think I will get my money back before I die!!


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## Lex Foutish (5 Feb 2011)

If you insulate the cavity, or use external insulation, it will take longer for the house to heat up. But it works by effectively turning your house into a giant storage heater. As you said, once you've heated the wall, the insulation outside it will cause it to hold the heat and give it back

If you insulate on the inside with insulated plasterboard, the room will heat up much quicker, but it won't hold the heat for as long.

Some people feel that, if the house is unoccupied during the day, you should go the insulated plasterboard route and, if it's occupied all day, you should go the external (or cavity insulation) route.


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