Extending for the future

[Crowbar hero]

Hi all, Thanks for letting me in!

We're staring down the barrels of our first demolish and extend.   We're a typical family of 4, living in a 3-bed detached 30's house, extending out the back with a new kitchen/diner, utility and 2 bedrooms.
We've actually been in the house 3 years now, despite moving in with a mind to extend the following summer (2019!), first personal and then current events have kinda gotten in the way, thus we've done very little to the place, there's still wood-chip on the wall, the kitchen is a horror-show (it will be demolished) and the bathroom is on the lowest threshold of bearable.  Photo's below of when we just moved in.
We have replaced the front glazing and door already, boarded the loft, and built a nice shed/gym at the top of the garden, so I've not been idle.
So here we are, we have planning permission, and a willing builder, looking to start around Easter time.. All previous quotes have been torn up and waved goodbye to given recent events, I'm waiting for the builder to re-quote.  I'll be getting stuck in as much as I can, I'm not afraid to get mucky, however I still need to balance a full-time job, and being a husband and dad as well.

Once we've completed the extension we'll move into it, and turn the tools to the existing house, renovating and re-arranging to suit the new layout - there's a chimney stack we'd like to dispose of, as well as partition walls to re-arrange - and lots of squeaky floorboards to fix.

Oh yeah, we'll be resident whilst all this is going on - at least that's the plan - my mum lives 15 minutes away, for emergency hot dinners and a bath if needed.

One of the features of the extension, is an attempt to anticipate what home life in the future will be, and if not designing in those features now, at least leaving the option for them without massive disruptive work later. Thus I'm looking seriously at underfloor heating, obviously downstairs, but upstairs as well, and then as a retrofit in the original part of the house once we've got the extension habitable. Given how energy prices are only going one way, having efficient heating is a must.

I've got plenty of questions to ask, even though our builder will be tasked with the structure and making it weatherproof, I'd like to identify and have time to think about potential issues before they become critical, so I'll be back on here, reading learning and posting a lot most likely.

 

cheers!

 

Edited February 15, 2022 by Crowbar hero
further detail added

[Marvin]

Welcome @Crowbar hero

 

As a basic, it's worth considering all the AIM APE elements at this stage, before making decisions. That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery,  and Air Source Heat Pump, Photovoltaics and Electric Vehicle.

 

You may not consider all of these, but when talking about saving energy on heating the first three make good long term choices

 

However 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 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.

 

Good luck with your project and remember the only daft question is the one you didn't ask and don't expect a good answer to your question unless you supply enough information.

 

Marvin

 

[Crowbar hero]

Thanks Marvin

One of my motivations for going fully UFH (eventually) is that I've read that ASHPs don't generate such high temperatures in the circulating water, and UFH typically works with lower temperatures, so getting rid of conventional radiators might mean we can still maintain a comfortable temperature if/when we forgo conventional combustion based heating.
I have concerns with airtightness as I believe a healthy living space is well ventilated. Some doofus has blocked the airbricks on the existing house (probably when they filled the cavity walls with fluff) so we have the issue of damp (many contributing factors) in some areas, thus higher than desirable humidity.  
I'm definitely into insulation - though the extension will be traditional bricks and sticks, I'm hoping to exceed wales current standards regarding insulation though careful material choice.  When I boarded the loft, I lifted the floor a bit (also to reinforce it) and applied extra rockwool, and then added another layer of insulation (Actis hybris) between the rafters.  This gives a semi-warm loft, which is ventilated naturally (due to it's being 90 years old) but with reduced heat loss due to the two stage insulation  - it also reduced the extremes of temperature, in the winter it's cool but not cold, and the summer is warm but not hot (pic below of it in progress).  I will probably try a similar strategy with the roof spaces of the extension, i I can get the layout I want.

I'll look into PV when the market is more established - I know a few people in that business so I hope I can get a good deal, but it's really only cost effective when combined with energy storage, as feed-in tarriffs are pitiful.

I don't have the pockets for an EV, my current motoring philosophy is to wring the last mile out of the current fleet  as I've worked out the carbon footprint of putting a new EV on my drive is equivalent to 2 years motoring in my 26yr old diesel.

[joe90]

Welcome @Crowbar hero, regarding ventilation MVHR will definitely cure your problem and also give the incoming air a temp boost, I have it and it’s very good. Yes UFH needs lower temperature water. I have a small ASHP that delivers 48’ water which is fine for DHW (with a larger tank to make up for blending down) and blended again to 30’ fir the UFH, the house is  a constant 21’ and very comfortable. It’s a different heat to radiators as they are hotter and you feel the heat coming at you. I totally agree with @Marvin above, you only buy insulation once and can only really make the build airtight initially. My builder was great regarding these matters but most need careful watching to make sure your standards are maintained. I look forward to your progress and questions, this is a great forum with oodles of great knowledge.

[Marvin]

Alot of big decisions depend on how long you intend to stay where you are.

 

In my humble opinion I think it would be a good idea to really understand how an MVHR works in reality. Ours for 100m2 floor area runs at about 20watts. So 0.48kWh a day. What it saves on heat alone is alot during the cold days.

 

When the air was 5C outside the heat exchanger was warming the fresh air to 19C

 

Our one comes on when the house is too humid as well.

 

It all looks good.

 

Good luck with your home improvements (no pun intended).

 

Marvin

[Crowbar hero]

1 hour ago, Marvin said:

Alot of big decisions depend on how long you intend to stay where you are.

 

In my humble opinion I think it would be a good idea to really understand how an MVHR works in reality. Ours for 100m2 floor area runs at about 20watts. So 0.48kWh a day. What it saves on heat alone is alot during the cold days.

 

 

I will read up on MVHR - though we are running into unknown cost territory for the build, and the pot is finite.

It's supposedly the forever house, it's a good area, decent neighbours, the schools are excellent and it's well positioned for access to Bristol (where I work) and Cardiff (where the wife works).  Beyond some pretty serious rises in sea level, I can't see us moving for at least 15-20 years.

[Crowbar hero]

1 hour ago, joe90 said:

Yes UFH needs lower temperature water. I have a small ASHP that delivers 48’ water which is fine for DHW (with a larger tank to make up for blending down) and blended again to 30’ fir the UFH, the house is  a constant 21’ and very comfortable. 

 

Thanks - these are useful figures to know.

[Marvin]

2 hours ago, Crowbar hero said:

3 hours ago, joe90 said:

Yes UFH needs lower temperature water. I have a small ASHP that delivers 48’ water which is fine for DHW (with a larger tank to make up for blending down) and blended again to 30’ fir the UFH, the house is  a constant 21’ and very comfortable. 

 

Thanks - these are useful figures to know.

 

Yes but remember this is with, I think, 200mm PIR insulation underneath the floor.