Beginner insulation questions - Getting jobs done in the right order

[Gill]

We've been in our new place for a few months now and starting to get a handle on how the house works (and where is doesn't). It's a  converted substation, now a single floor bungalow with plenty upgrading required. I'm not sure if I'm getting things in the right order so was hoping for some guidance. 

 

 We've got an uninsulated suspended floor with crawl space under the house so insulating that is high on the list. It's fairly likely we'll change heating (electric storage heater) & DHW (immersion) system in time but until we've insulated I've no idea what our heating needs might be. If we did end up going ASHP next year would it be simple enough to remove and refit the insulation as needed? Would that favour mineral wool insulation over boards?

 

Also appears that the cavity wall is uninsulated.  Under the house is well ventilated but we're not on mains drainage.  Should this be a concern? Cavity wall insulation seems to be a topic with polar opposite opinions concerning damp. Our last place had no issues but I can't help wondering why the previous owner didn't get it done. 

The other priority is new windows - any benifits to doing this before or after cavity wall insulation? 

Any pointers appreciated. 

[Temp]

3 minutes ago, Gill said:

Cavity wall insulation seems to be a topic with polar opposite opinions concerning damp. Our last place had no issues but I can't help wondering why the previous owner didn't get it done. 

 

It depends on the type of insulation, the porosity of the bricks and exposure to wind driven rain.  I think the concensus on this forum is that the grey coated bead systems are less prone to issues than loose fibre fill types. But I'm sure someone will correct me if I'm wrong.

 

Is the outside brick or render? If its render in good condition then that can virtually eliminate the risk of damp because the render stops water getting into the outer leaf of bricks. 

 

8 minutes ago, Gill said:

It's fairly likely we'll change heating (electric storage heater) & DHW (immersion) system in time but until we've insulated I've no idea what our heating needs might be. If we did end up going ASHP next year would it be simple enough to remove and refit the insulation as needed? Would that favour mineral wool insulation over boards?

 

ASHP work best on very well insulated houses. The flow temperature is lower than for a fa's or oil boiler so you either need UFH or bigger than normal rads. You wouldn't normally "change" the insulation when fitting ASHP, but you might add to it instead.

 

Mineral wool vs PIR... if you just compare the raw material PIR is a better insulator for a given thickness. But it can be harder to install between joists or rafters because it has to be cut exactly to size or gaps foamed to seal them. Mineral wool can be compressed a bit to fit uneven gaps. You might consider putting mineral wool between the floor joists AND then PIR under the joists where sheets can be butted together without having to cut them. Butt joints can be tapped to improve airtightness.

 

If you want UFH then that works best with tile or stone flooring. Carpets and Engineered wood can be used but a bit more care is needed. 

 

If you have the headroom an UFH system that goes on top of the existing worp floor might be worth a look. You would still put most of the insulation below the floorboards though.

 

 

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[JohnMo]

Windows depends on whether double or single glazed.  Windows generally are quite small area, so may not be that high on the list of priorities. Concentrate your efforts on insulation first its way cheaper bag for your buck.  Also important is elimination of drafts.  Floor as suggested mineral wool between joists and sheet material under.  25mm sheet is easy to handle can be screwed to the joists with screws and penny washers.  Between joists something like Rockwool Flexi will stay in place quite well while you sheet out.

 

There's nothing wrong with storage heaters, as you reduce the heating demand, the storage heater start to perform better as they have to do less work.

 

Loft get about 350mm in there, but don't close of vents at top and bottom of roof.

 

 

[Marvin]

Hi @Gill

 

It worth considering all the AIM and APE elements before making decisions. That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery, and Air Source Heat Pump, Photovoltaics and Electric Vehicle.

 

Some of these will not work properly without the others:

 

1. A MVHR will not work properly without Airtightness.
2. An Air Source Heat Pump will have to compensate for the lack of Airtightness and/or Insulation to the degree that the benefits become questionable, especially during winter, without them.
3. An ASHP uses electricity and Photovoltaics can supply a little during winter and a lot during summer when cooling can be a problem and an ASHP can supply cooling.
4. PV can supply a little to an Electric Vehicle during winter and plenty during summer if your vehicle is at home during sunny days.

So if finances cause you to have to consider only a few in my humble opinion AIM first and go APE later. (but prepare the property for the APE works as much as you can).

 

Best of Luck

 

Marvin

 

[Gill]

Thanks a lot for all your advise.  Starting to form a clearer picture now of what the right focus should be.

tldr : Think my focus on underfloor insulation / windows / draft proofing & getting someone in the know to asses the brick work on the house before we look at cavity wall insulation.  

 

 

@Temp The outside of the building is a combination of brick and render.  We've done some basic repairs to the render and it looks in decent shape.  The brick work I'm not so sure on - it's pretty dated.  That said, although we're west cost of Scotland the house we've not had driving rain.  For the brickwork i'm assuming that's something I should get assessed.  I could diy some mortar where it looks loose but I'll assume it needs someone in the know to assess suitability for cavity wall.  We seem to be a bit protected from the worst of the west of Scotland weather but then we've only been in the house 5 months so I'm probably kidding myself.  

I may try to tackle the underfloor but probably after I look at a quote or too.  The crawl space drops down further down the house and I can only imagine it'll take me weeks to do something those in the know could do in a day.  I like the idea of PIR under the joints but the service pipes and cabling are making me thing that part will be the most difficult.  

As for fitting a new heating / DHW system - we're electric only so ASHP / UFH or oversized rads would require plumbing which is where my concern about insulating first came in.  If I understand correctly, it shouldn't be a major issue if we do need change the service pipes down the line.  

 

@JohnMo  We are large window rich - which is great aside from the drafts.  Pretty much even room has at least 3m sq of window.  They are all DG wood framed but more than half the panels are blown and when the weather took a turn for the cooler last week there was a substantial amount of condensation on the inside.   We're also near a busy road and additional sound insulation is definitely something we need.  I'm hoping 3G and additional insulation helps with both noise and heat retention.  Looking under the house, it might have to be sheet under insulation due to the cluster of service cabling and pipes  (this might be perfectly normal but looks untidy to my untrained eye).  Loft we're good with +400mm insulation that hasn't covered the vents.

 

@Marvin MVHR was on my consider list given that the attic isn't converted so less of a challenge than in some properties.  I've been doing a lot of reading trying to work out if we could get the property to a standard where it would benefit.  That said, we have an internal wet room with a useless extractor fan that's going to need attention as the tiling grout has failed and the paster board behind has gone.   A good ventilation solution will be needed in there.  I guess it's a decision for next year after we sort out immediate concerns.  PV is also one of my research areas as we're electric only, large south facing roof, immersion water.   I'm thinking if we can diver power to HW storage that would be a win.  Maybe battery cost will come down in time to make that another feasible option.  Budget wise, I'm sure we can tackle window, insulation and airtight unless the prices double again.  MHVR could potentially go in there too but I think i might need to get into the realms of measuring heat loss before making a call on that.  

 

On the off chance it interests anyone I've added a couple of pics of the underfloor space and the outside render / brick.  I'd be interested if any more critical eye can see any red flags (aside from the underfloor mess 🙂).  

 

Cheers.  

[JohnMo]

The crawl space looks like a 70s house we owned, I looked and worked on something else and never went back (that was 20 years ago).  No-one can see it, so who cares if it looks pretty said the trades men.

[Gill]

10 hours ago, JohnMo said:

The crawl space looks like a 70s house we owned, I looked and worked on something else and never went back (that was 20 years ago).  No-one can see it, so who cares if it looks pretty said the trades men.

Unless insulation quotes come back surprisingly high, I suspect i may do similar. There's no shortage of jobs I can do on my list. 🙂