Retrofit underway - prepare for questions....

[GP41]

We are in the process of a not-too-deep retrofit and I'm really pleased to have stumbled across this forum through some of my recent internet searches.  It looks like it's going to be a really valuable resource and somewhere to share our progress. So here's my intro - you'll need a cup of tea and a couple of bourbons.

 

We have a 4-bed, 180sqm, 1960 detached house.  It started off smaller than that and in 2010 when we moved in, we set about designing an extension.  Completed that work in 2013 and have lived in it without so much as a drop of paint ever since.  Just over a year ago, fuelled by an interest in houses that were appearing on Grand Designs that were basically existing passively in their environment with minimal carbon footprint, and keen to get to a place where we had taken full control of our home and its energy expenditure prior to retirement, we set about finding ways to improve.

 

First off was reducing energy consumption and just being much more aware of what we use: a tired old dishwasher that I'd kept hobbling along with fixes and a past-its-best beer fridge in the garage went first, plus ensuring all lights were LED (apart from some stubborn under cupboard lights in the kitchen that we've still to find replacements for); also ensuring that, particularly  older, devices were not left on standby.  Replacing a broken washing machine also made us realise just how much more inefficient older appliances are.

 

Some time ago we'd installed Honeywell Evohome TRVs on all our radiators.  We were fed up with a central thermostat never getting things right.  We'd either be downstairs all evening with it and go to bed in a cold upstairs, or sit overheating downstairs with the house cosy upstairs.  Working from home a lot, I also always felt I was heating an entire house when I spent all day in one room.  I know they are not everyone's cup of tea but it knocked 10% off our heating bills and has more than paid for itself now.  I suspect as we move to a heat pump they'll become nothing more than a per-room temp sensor with the house heated more uniformly.

 

Back in September 2022 we organised an assessment that included a door blower test.  It highlighted a number of areas for improvement, in particular insulation, draughtproofing and windows & doors.  Our air permeability figure was just under 7.  We set about massively improving loft insulation to 3-400mm - including use of eaves ventilation to avoid issues up there.  We made the loft hatch insulated and more airtight, and generally resolved quite a few draughty areas.  Many of the windows and doors were in a poor state so we've temporarily draughtproofed them with foam tape until we replace them.  We drew a line at any further draughproofing until we've put in proper ventilation (I know there's some chicken and egg here).

 

I've bought a FLIR camera which has been amazing, both in terms of highlighting problem areas and in showing us how much improvement we've made as a result of a particular intervention. It has highlighted some things that we are probably just stuck with (e.g. that classic issue at the top of outer walls where the inner leaf of the cavity is exposed to the outside with no simple way of continuing insulation from wall to ceiling, or where RSJs up in the cold loft rest on the ceiling acting as thermal bridges).

 

Finally, over a year ago, we installed a fairly substantial solar & battery system.  13.6kWp of PV on an east/west split with 27kWh of battery storage.  This has been amazing.  We overcooked the battery sizing (at the time you could only get the VAT off if installed at same time as PV, but that's since been dropped) but were futureproofing in readiness for further electrification of the house, in particular an induction hob and heat pump that will enable us to disconnect our gas meter.

 

So where are we know?  We're moving forward in several areas:

• We are in the process of designing an MVHR install.  Had one false start working towards a design that involve significant rigid ducting in a loft space.  We've backed out of this now and are close to settling on a revised approach using semi-flexible ducting in a radial configuration passing through voids within the thermal envelope.
• We are in the process of the spec/quote for a heat pump.  We'd originally planned to do this for next winter but our 17 year old combi isn't behaving and I refuse to spend any more money fixing it.
• We're researching induction hobs that include downdraft recirculating extraction to appease the MVHR.
• We are getting quotes to replace windows.  Windows in the front of the house are all over 17 years old, double glazed uPVC, badly fitted and poorly performing. In the back of the house, we've slightly updated uPVC, fitted just 12 years ago, but not fitted well.  Whilst they still look really good, they are cold & draughty.  We are looking to replace with alu-clad wooden triple glazing throughout. Sadly these are just one example of things that "if we'd known then what we know now" would have been a different product fitted properly for a small proportion of the cost of replacement now.  From a performance perspective, the extension work is poor. Looking at some of the photos I took during the build, I can now see issues like badly fitted cavity batts, gappy, not taped, and in one or two places, sections missing - just makes me cringe.  It would have taken a small amount of extra effort to have done it 'properly' at the time. As a result, I think the original 1960 build probably performs better in many ways, even whilst having a narrower cavity (filled with that pumped-in fluffy stuff but which according to our assessor still seems to be offering good coverage fourteen years on).
• We can resume work on airtightness soon.  As well as getting properly fitted windows, key areas include: new seals on the Velux windows; work on the suspended ground floor (ideally without disturbing lots of Amtico flooring...), remedial work on a first floor room that is positioned above an integral garage, sealing first floor joist gaps and dealing with cracks in plasterboard joints.  I'd love to know if there is a simple solution to this that doesn't involve ripping down entire walls of plasterboard.  I could just fill them with a sealant but I don't know how long lasting that would be. I'd like to apply airtightness tape but that would mean taking back the skim coat of plaster, fitting the tape to the boards and reskimming - am I missing something?
• I'm considering further insulation options, both in terms of under the suspended floor but also walls.  The cost of EWI seems prohibitive and I'm sure I've read that with cavities it can be ineffective and potentially damaging.  We could just apply IWI to some 'problem walls'. I can see I'll be spending a lot of time searching threads in here.

Overall, ideally I'd like to get us nearer to a permeability figure of 4 to increase the benefit of the MVHR.

 

With all these things, the challenge seems to be the order in which to carry out this work with so many interdependencies and inevitably compromises to consider, alongside the usual considerations of cost and disruption vs benefit.  Equally, I don't want to do things 'piecemeal' and find out there was a better way when looked at holistically.  Finding a professional who is interested in that is difficult.  Architects aren't interested because it's not a half a million pound fancy new build, individual trades are only interested in their specific field (understandably so) and from my brush with a seemingly very competent expert, they didn't seem particularly interested in 'joining it all together' or helping to devise a workable plan, just in charging on an hourly basis to answer questions you throw their way.  So here I am, making my own way. I'll no doubt be along with some very specific questions but if anyone has any initial thoughts, I'm open to constructive criticism and suggestions!

 

If you made it this far, thanks for reading!

[Conor]

Well done on the work so far, and welcome. You're saying all the right things and I think your approach is spot on.

 

Why timber windows? Double the price of aluclad PVC for no real benefits.

 

What is your floor construction? Any scope to insulate?

 

 

[GP41]

11 minutes ago, Conor said:

Well done on the work so far, and welcome. You're saying all the right things and I think your approach is spot on.

 

Why timber windows? Double the price of aluclad PVC for no real benefits.

 

What is your floor construction? Any scope to insulate?

 

 

Thanks for the welcome @Conor.  I was just looking for longevity for the windows.  I'd also just rather not use plastic - we've not had great experiences with uPVC and ideally, I don't want to be doing this again. Would aluclad plastic offer the same insulation as aluclad wood?

 

The ground floor has three parts to it:

- the original suspended floor that I would like to insulate the way I've seen in the ecological building systems way Suspended Timber Floor Insulation: From Above Installation Guide (Method 1) | Ecological Building Systems.  

- the original concrete floor (no insulation) - small area of original kitchen slab that we will probably have to live with.

- new concrete floor that we have 100mm of celotex in (laid to regs back in 2012).

 

There's also a section of boarded first floor that sits over the integral garage and I'm considering  the ecological building systems 'from below' method so that I can seal the garage out of the house and insulate that floor at the same time.

 

We've been considering various options for the floors, particularly because it currently makes it less sensible to fit UFH on top of, and that might have been a good match for the ASHP.  However, we've a substantial area of the floor, including some of that suspended floor, covered in Amtico (laid on levelling compound on screwed down plywood) that will just be an expensive nightmare to lift, throw away and replace. I don't think there such a thing as a lift and relay of Amtico...  

 

So we are stuck here right now.  I just don't know what the best option is.  I've heard of people spraying insulation through some remote controlled device from underneath.  The thought of sealing the underside of the floor that way fills me with a similar amount of dread as the thought of sprayfoaming the underside of the rafters in our loft and we know where that's got people!  I'm also concerned about the radiator pipework that runs under there.  It's going to be needing additional insulation as that void gets even colder. That's assuming it has to run under any underfloor insulation.

 

Any ideas?