Upgrading the house heatwise

In January 2005 I had an infrared survey done of the house by a professional whose day job was decommissioning nuclear power stations.  Last year someone at church did an EPC (Energy Performance Certificate) for us.  We were at the bottom end of a C rating. We achieved a C due to our solar panels, an energy efficient boiler and (mostly) old double glazing (see my post on double glazing paying for itself).  The EPC report made three recommendations.

  • Upgrade the windows.
  • Insulate under the floors.
  • Insulate the walls.

At the beginning of the 2023 we upgraded the windows in the coldest room in the house (ironically the newest – built in 2000).  This dramatically improved the situation.  Also we replaced the 1995 era window in the bathroom which is the highest in the house.  This also helped.  In November we replaced all the windows upstairs other than the new bathroom one and the kitchen ones downstairs.

In addition I’ve started on the walls and floor.  We live in a conservation area so insulating the outside stone walls is a non starter (even if I wanted to), but the kitchen is a narrow galley type that pokes out the back of the house.  One side is a party wall with our neighbours and at the end is the 2000 extension used as an office/spare room.  The whole thing is brick covered in render.  My aim is to remove the render, insulate it and cover it with silicon render.  Part of the wall is inside an unheated conservatory and I was going to start with this since the outside will require at least a building warrant – if not that and planning permission.  In October I went on a a day course to learn how to do this since I can’t get anyone to do what is a small area.  The problem is at the moment there’s a leak into the conservatory and until that’s fixed I can’t start.

In September I made a start on the floors.  We want to have the wooden floor in the hall sanded, so this seemed like a good opportunity to insulate under there – something I’d had a half hearted go at some years ago.  This time I was serious.  I’ve done the lot.  I did it myself partly to save costs and partly since I couldn’t find anyone else to do it.

The EPC gives links to general advice on the suggested measures they suggest.  There are two recommended methods to insulate floors.  The first is a robot that sprays a foam onto the underside of the floor boards.  I have concerns about its breathability, but in any case its expensive and requires good access and a level surface.  Under our floor it looks like the surface of Mars with rubble everywhere and there are pipes and wires to obstruct its progress.  In the end I used the other recommended method which is to suspend insulation between the joists.  There is no issue with damp since it’s on the cold side (imagine if you flipped it 180 degrees and it was above lying between the roof joists). 

Part of the hall floor and downstairs toilet completed.

I also did under the floor of the adjoining toilet since we decided we’d go back to bare boards there too.  In doing so I discovered worm and a leak at junction of the waste from the sink and boiler.  This was sorted out by plumber who at the same time replaced the sink down pipe (lead) and toilet waste pipe (rusting cast iron) with plastic. Both were ‘cold bridges’ so this and the insulation have largely sorted out condensation gathering on the toilet cistern.  I’ve treated the worm.

This made a massive difference to the hall temperature.  10-15% is lost through floors – less than walls, but in the hall there is very little external wall (the toilet is tiny).  After I’d finished the floor I cast around for other places to insulate.  The new window in our lounge helped, but it still didn’t warm up quickly in very cold weather.  The lounge is a particular challenge.  Like the rest of the house (other than the kitchen/extension) its formed of solid stone walls.  It’s above our neighbours lounge and extends out from the house with one totally external wall and two others that are about 60% external.  From the inside the window looks almost like it’s a bay window although its not (see images below).  Below it was a wooden panel which when I tapped it sounded hollow and it’s the thinnest bit of wall (approximately half the thickness of the rest).  I reasoned there was considerable amount of space between the wood and the stone and I could insulate behind it.  The panel was two tongue and groove floorboards and took me a couple of hours to remove.  The image below shows the mess behind it (complete with 1917 newspapers and a number of wine corks). 

Below the lounge window. What I found.

I cleaned it out, re-pointed the worst of the mortar with fresh lime and packed insulation in it, then put the wood back and repainted bits of it. 

After re-pointing with lime. I re-pointed some of the outside with lime last summer so it should breathe very well.

This small area heatwise has made the biggest single difference other than the roof insulation.  I’ve monitored the temperature in the room for years and this and the new double glazing has raised the temperature by 2-3 degrees.

Post insulation. I stuck the front page of the Guardian in.

In the last few weeks I’ve stuck reflective insulation behind all the radiators, sorted out drafts using sticky draft excluders, made the homemade conservatory to kitchen cat flap less leaky and added a bit more insulation onto the roof hatch.  The company that put our new windows in replaced a vent in the kitchen window which had broken and was drafty.  Today we put in insulated blind over our front door.

What have I learnt?

  • I was rather overwhelmed by the infrared survey.  Insulating walls and floors seemed both expensive and difficult.  High energy costs and the need to put in a heat pump at some point in the future have made me revisit it.  DIY is relatively cheap however.  I’m intending to insulate under at least one more room downstairs.
  • Everytime I do something major on the heatwise side of things the comfort level in the house moves up a level.  I’m monitoring the gas bills to see how much difference it makes although this is not easy since the use varies from day to day much less month to month.
  • Small things can make a disproportionate difference. 

My aim is to get the house to a B rating.  An A rating is likely unachievable due to its solid walls.  Since the EPC rating we’ve bought an EV which has doubled our electricity use.  Ironically this will lower our EPC rating?!  But that is for a future post.




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