Insulating internal walls in main living space : reduce energy usage+loss? Foolish?

ReadySteadyGo

Hi,

I am not sure where the best question is to ask questions about insulation - sorry if this should be in construction/BER forum?

In the main living space in my house, there are two external wall, a party wall, and a solid internal wall. The two external walls have windows with very good u-values in them. Beyond the solid internal wall is the hall + stairs. Beyond the part wall, is next doors living space and kitchen space.

I want to insulate this space as much as possible. I am installing ~100mm of internal drylining on the two external walls. I am considering putting insulation in the ceiling (i have a thread in the BER forum about that http://www.boards.ie/vbulletin/showthread.php?t=2056059984).

The space will be zoned on the central heating.

I have been told that there is no point in insulating a party wall, as you will gain the same as you lose. is that through even for a hollow brick wall?

I was considering insulating the solid internal wall, on the side facing into the living space.

I am not interested in heating the hall, stairs and landing. and I will only be able to put minimum insulation on the external wall (beyond the internal wall) along the stairs,

It makes sense to me, as I will spend most of my time in this living space, so insulating, will keep it warm for longer, and require less energy to heat it.

Is this a bad idea to insulate the internal walls in living spaces?

antoinolachtnai

I don't think insulating the wall will make much difference because the temperature differential between the two sides of the internal wall will be very little. Insulation only helps when there is a differential between the inside and the outside of the wall. On an external wall, the differential will often be 15 degrees between inside and outside and sometimes higher. On an internal wall, the differential is extremely unlikely to be more than 7 or 8 degrees, assuming you have it will draughtproofed.

Sometimes people do this sort of insulation for the sake of soundproofing.

Much the same goes for the ceiling.

I do not think you will get any return on your investment from this type of insulation, i.e., the cost of the insulation will be more than the cost of the heating you will save.

In your situation, it is well worth draughtproofing the internal doors, however and making sure the ceilings and walls are completely sealed.

Carlow52

I disagree so much with the previous post that I wont bother taking issue with all the basic errors therein.
I will return to this after dinner

paddy147

antoinolachtnai wrote: »

I don't think insulating the wall will make much difference because the temperature differential between the two sides of the internal wall will be very little. Insulation only helps when there is a differential between the inside and the outside of the wall. On an external wall, the differential will often be 15 degrees between inside and outside and sometimes higher. On an internal wall, the differential is extremely unlikely to be more than 7 or 8 degrees, assuming you have it will draughtproofed.

Sometimes people do this sort of insulation for the sake of soundproofing.

Much the same goes for the ceiling.

I do not think you will get any return on your investment from this type of insulation, i.e., the cost of the insulation will be more than the cost of the heating you will save.

In your situation, it is well worth draughtproofing the internal doors, however and making sure the ceilings and walls are completely sealed.

Can I ask where you have been living for the past few years?? with regards your opinions.

Totally wrong.

paddy147

I had my entire house gutted and internally insulated and sound proofed too.All internal walls,ceilings,downstairs,upstairs and attic space too.

Also had a brand new zoned central heating system and boiler installed and a Stovax Riva 66 inset stove installed too.Snug as a bug in a rug,barely use the central heating now,as the heat stays in house for so long now since it was insulated.

Oh,and feck all heating bills now too.Roll on winter time so.:D

antoinolachtnai

paddy147 wrote: »

Can I ask where you have been living for the past few years?? with regards your opinions.

Totally wrong.

So how long would it take to reoup the cost of insulating an existing well sealed interior wall? How long would it take to recoup the cost of insultating an existing well-sealed ceiling (below roof level)?

paddy147

antoinolachtnai wrote: »

So how long would it take to reoup the cost of insulating an existing well sealed interior wall? How long would it take to recoup the cost of insultating an existing well-sealed ceiling (below roof level)?

The chap is asking about if its worth insulating his living space with regards heat and comfort...........read what he is asking again.

Then look at what you posted.

antoinolachtnai

He wants to keep it warm for longer and reduce the energy needed to heat it. I presumed from this that he had an economic motive.

But if comfort is the issue: if he has gas heating and the heating is 66 percent efficient, he will be able to put 16 KWh of heat, equivalent to two twin bar electric fires on for 4 hours a day, into the room for 1 euro per day. If the external walls are moderately well insulated and there are no draughts, this will keep him pretty comfy, especially if the house is unoccupied for part of the day. He could do this for 120 days a year for 8 years and it would still cost him less than 1000 euros. He would be lucky to buy the insulation, pull up and relay all the floorboards on top of the insulation, attach the wallboards, replaster, and pay the cost of capital for that low a price.

ReadySteadyGo

Thanks for all the feedback. I do have an economic motive. And If it improves comfort all the better.

I will have an a-rated gas condending boiler, so it should be 90% effecient.

The wall in question (about 4m with a door in it) has to be scored and skimmed at a minimum already. So the extra cost would be some extra insulated boards, fixing them on the wall. let's say 4 boards@30 euro each and an extra 30 for labour (on top of existing jobs), supply and fit a new door architrave (no idea here - lets say 150 euro and I might be replacing that anyway ). so total extra price is ~150-300 euro.

Given a heating estimate of 120 euros a year for the space. It would have to reduce heating requirement for the room by 10-20% to get a 10 year payback.