A B C?

[PrincessB]

I've always wanted to build a house, so I'm in full on design mode planning my next dwelling.

Nothing is going to happen till next April when a few things will start to move forwards, so no rush.

I am of course, utterly confused, I've done extensions, I've done the drawings for planning permission, worked out internals and that sort of stuff, but I've never tasked myself with designing an entire house.

As I've got to start somewhere, I've been looking at the energy efficiency ratings and going nowhere fast, hence the questions:

I think my Victorian cottage (after quite a bit of TLC) will hit a 'C' Rating.

For a new build, I'd much rather aim for a cost effecive 'A' rather than the full on 'money is not an obstacle' Passivhaus standard. Quite happy to use some of the techniques but a bit relucant to go overboard. Whole house ventilation, saline ground source loops, tiny windows set back into two feet of instulation.

Finding out how they calculate the EPC has become a bit annoying. I can't find the actual criteria they use to score points, so I'm in a position of not knowing where to start:

I'm not after scraping an A, as a build to sell, I'm just trying to set out some criteria to meet.

Help,

B.

I will want a big solar array to power the house and charge the car but that's part of the planning I can do.

[todthedog]

Princess, have a look at Navitron Renewable Energy And Sustainability Forum.
Loads of folk willing to help on that part of your journey, a few off gridders and self builders. I don't think I'm allowed a direct link but if you have a problem pm me. Good luck.

[twotwo22]

Might be the best way to find out and just 'price it in' to the build.

https://quodox-training.co.uk/product-c ... gy-courses

[todthedog]

Read up on Passivhaus here is a starter site.

http://www.passivhaustrust.org.uk/

Building from the start it should add less than £10,000 to the overall cost to build to near passive house standards.

The EPC ratings can be very misleading and unless the rating has been done by someone who knows what they are talking about, not attending a brief course to enable them to offer certification.

I have seen an EPC that suggested as an energy improvement could be achieved by taking up the existing concrete floor, insulating and then replacing.
Cost 20K savings per annum £250. Bonkers


https://www.energysavingtrust.org.uk/ho ... HIQAvD_BwE

Do your research insulate, insulate, and then insulate. Seal gaps. There I've just saved you £1000 on an EPC course

It is far cheaper to pay a little more when building than try and retrofit.

[dspp]

Done properly Passivhaus saves money by eliminating stuff, such as oversized heating systems. So don't diss going for A+ or Passivhaus.
http://www.passivhaustrust.org.uk/

The EPC calcs are refreshed quite frequently which is why you can't just learn it. BRE is the custodian.
https://www.bregroup.com/sap/standard-a ... -sap-2012/
https://www.bre.co.uk/acd/page.jsp?id=1634
https://www.bre.co.uk/page.jsp?id=706

Insulate insulate insulate, and seal. Remember to put as much insulation as possible on the outside, and expose the inside to the thermal mass. That way you won't get wild air temperature swings indoors.

regards, dspp

[PrincessB]

Insulate insulate insulate, and seal.

Hi dspp.

This is where I continue being confused and I hope you can help me out here.

Two areas where some kind of external venting would be desirable are the cooker hood and any bathrooms, especially those with showers, though smells are always best vented out of the room.

A whole house ventilation system would be fine for the bathrooms as I understand the humidity on the return will kick the fans into high mode and of course heat will be recovered.

I don't understand how this would work in the kitchen? I worked out that on full blast, my commercial cooker hood is capable of performing a complete air extract from the kitchen/diner every six minutes.

Don't understand how we can marry sealing with ultra ventilation.

B.

[PhaseThree]

I've just completed a Passive-ish spec build to my own design, and may be able to offer some pointers.
Firstly don't get hung up on EPC it tells you nothing about the energy consumption or livability of your house. To a first approximation you can get an "A" rating for a tent if you can assocate it wih a large enough solar PV array. (There are unmodified farm houses with very high EPC ratings because their barn has a 22kW PV array).
The EPC on a new build is an output of the SAP measurement process. This takes into account things like U-values of walls, floors, window, roof etc along with air tightness. I used the Stroma SAP software to model my build and work out the tradeoffs, its a steep learning curve but well worth it.

You can download it (free) from here
https://www.stromamembers.co.uk/downloa ... ublish.htm

To answer your veniltaion questions - We use an MVHR system which provides whole house ventilation while conserving most of the heat. Ventilation boost is triggered on humidity or by boost buttons placed in the bathrooms and kitchen. (You can also trigger such systems when lights are switched on etc).
The trick with the kichen is to use two stage ventilation :- At the cooker you use a recirculating ventalation fan which scrubs greese and most smells out of the local air, this can be done with an overhead unit or a downdraft unit. The scrubbed air is vented into the kitchen then replaced by the MVHR running on boost. Works well in my experience.

[PrincessB]

Another question dspp (and the other helpful Lemoneers!)

Insulate insulate insulate, and seal. Remember to put as much insulation as possible on the outside, and expose the inside to the thermal mass. That way you won't get wild air temperature swings indoors.

I didn't think this one through properly when I had the extension built, the result being (from outside to inside):

Render
Breeze block
Insulation (enough rockwool to meet regs)
More breeze block
Plasterboard and skim.

If I'd wanted to go for thermal mass, in hindsight I could have spent a few pennies more and had,

From the outside in:

Render
Breeze block
A greater thickness of rockwool.
Big old heavy bricks or something equally dense.
Wet plaster

The second option would have taken a medium room (400 square feet) from the current low effective thermal mass to a higher level. The downside to me would be the amount of moisture trapped in that high thermal mass, without proper power ventilation a hot spell bakes the moisture out of the the walls and the humidity goes up to the point of discomfort.

On the first option (which I used) I underpowered the radiator ratings (by mistake) - Despite being a low thermal mass room, it takes an age to warm up if I've been away for a few days during a cold spell. Higher thermal mass would make that worse.

Just wondering what solutions you or anyone else have used.

Regards,

B.

[PhaseThree]

Thermal mass is a bit of a red herring. Most Passive spec houses are built of timber frame - A lot easier to get rid of thermal bridges than in block built houses. The effectiveness of any thermal mass reduces the further it gets away from your internal air. In reality a decent plaster layer will provide the majority of the effective thermal mass irrespective of what's behind it.
What you are looking for is significant levels of insulation and airtightness to keep whatever heat have in the house and to stop it leaking out. The other factor you are looking to control is decrement delay. This is the speed at which heat transfers from inside to/from outside, ideally you want to design in a delay of around 8hours. So the warm daytime heat warms the house in time for the evening.

There's lots of good stuff on this site on the subject.
http://www.greenspec.co.uk/building-des ... ent-delay/
http://www.greenspec.co.uk/building-des ... rmal-mass/

[PrincessB]

Massive thanks to all and everyone who has contributed links and opinions to this thread.

At the moment, I feel a bit like someone starting a second hand jigsaw. Some of the peices are still connected to the others, most of the others are knocking about in a big pile waiting to be slotted into place.

I've got a rough idea of where I want to get to in terms of build size, and certain rooms are designed and can be slotted in like Lego(tm) bricks. Other aspects are a part of the puzzle.

I'm pretty good with 3d spaces, heat load calculations, designing a kitchens that both works (and look good) with the right lighting levels.

I'd like to ask quite a few more questions over time, I'm finding there are areas I know so little about that I can only quote about known unknowns and unknown unknowns.

Once again thanks,

B.

[todthedog]

Have you considered SIPS?

https://www.homebuilding.co.uk/guide-to ... ed-panels/

[sg31]

My house was built in the mid 60's if mainly double skin brick and a 50mm cavity, at some later stage the cavity was insulated. The main problem we had was that the large gable end was south facing and catches the sun. The bricks heat up during the day and radiate the heat out at night. The main bedroom rund the full lengeth of that wall and was unbearably hot in summer. You can feel the heat given off by the wall a couple of feet away as you would from a fire.

When we renovated and extended the upstairs the upstairs we had all the plaster off all the walls battened them applied YBS superquilt..

https://www.superquilt-insulation.co.uk ... gK94PD_BwE

then it was just cross battened, platerboarded and skimmed. It's by far the least labour intensive form of insulation I've used.

The effect is everything we hoped for. The room is much cooler in winter and warmer in summer.

Maybe this is something to consider.

(Don't be put off by the price, shop around deals are to be had on line and it was woth it to us)

[todthedog]

Alternatively buy plasterboard with insulation foam pre attached and stick or mechanically fix to your existing wall. Tape and joint and you are done. Very little mess.

Your room would be cooler in Summer, warmer in Winter!

[quelquod]

The effect is everything we hoped for. The room is much cooler in winter and warmer in summer.

Really? And here’s me thinking everyone’s was like that (ours is!).

[sg31]

The effect is everything we hoped for. The room is much cooler in winter and warmer in summer.

Really? And here’s me thinking everyone’s was like that (ours is!).

OK, My mistake, I hold my hands up and beg forgiveness. It should read ...much cooler in summer and warmer in winter.

[DrFfybes]

The effect is everything we hoped for. The room is much cooler in winter and warmer in summer.

Really? And here’s me thinking everyone’s was like that (ours is!).

Ho ho - I missed that one.

My mum's wasn't though. She systematically refused to have heating on during BST irrespective of the actual temp, but once the clocks went back the stat rarely dropped under 22 degrees. Now she is late 80s she has seen sense and just has it on 20 all year around.

Paul