Hello. Just starting ideas... so many questions!

[MLR1907]

Hello all,

 

Thanks in advance for this forum, we’ve just started mulling ideas for a self build and what it might entail and I’ve already found many posts helpful.

 

I just wanted to say hello mainly, I will try and post questions in relevant areas but the general idea is we want a large-ish (275-280sqm) house over two floors that looks like a traditional stone built house but which performs to modern, green standards (thinking air tight, MVHR etc)  is ready for the addition of children (also in planning stages!)

I’d like to be super green but the other half worries about running out of hot water and cold floors if the heating doesn’t need to be on much! ?‍♀️ On the surface some seem like trivial questions but the longevity of being comfortable in our home is important and I’m sure several of them actually lead back to the fabric of the house being correct. 
 

I’m fairly hands on and pretty competent at DIY having just renovated a 200 year old cottage, the other half not so much! 
 

Like I said, I’ll try and post questions in specific areas but any general advice for where to start is greatly welcomed!

 

Cheers

Morgan

[SteamyTea]

Welcome.

Get a good book about physics.

The two main areas are material properties and thermodynamics.

Both only require basic arithmetic, so no need for a maths book.

[Iceverge]

Welcome. 

 

I keep directing people to this but have a look at the Green building store denby dale passivhaus you tube video's. 

 

In my opinion 30-40m2 per person is generous living space. With cleverly placed windows it will feel much larger. 

 

@TerryE has a good setup for what you're after. A traditional looking house build to modern standards. Timber frame is only one way to skin the cat though.  

 

Be careful of all the greenwash out there. An very large poorly built house with a high heating demand and a few bolt on "eco" bits and pieces will do more harm to the environment than a conservatively proportioned smaller dwelling built properly to the building regulations. 

 

 

[SteamyTea]

11 minutes ago, Iceverge said:

 

In my opinion 30-40m2 per person is generous living space

I take it you don't live in that size space. My house is around 50m².

Don't leave much space for storage. Hard to find a place to store a bike, a ladder, hobby stuff.

Just my book shelves take up 1/30 of my usable space.

[Iceverge]

Until last week we were living in less than 60m2. It was tight but perfectly adequate when we were 2 not 3.  

 

For all that junk a shed or storage unit will do.  My neighbour was hauling stuff into his attic last week at his partners behest. We mused that what he really needed to do was to install a hatch in the gable end of the attic through which he could dump said items directly into a skip. People have too much stuff I reckon. 

 

“The more things you own, the more they own you.”

― Chuck Palahniuk, Fight Club

Edited March 2, 2021 by Iceverge

[jack]

29 minutes ago, Iceverge said:

Until last week we were living in less than 60m2. It was tight but perfectly adequate when we were 2 not 3.  

 

We lived with two young kids in less than 90m² for two years. More space would have been nice (especially the tiny kitchen), sure, but living in a place that's three times as big is not three times as good. If I were building again, I'd at minimum tweak down the sizes of a few rooms.

 

31 minutes ago, Iceverge said:

“The more things you own, the more they own you.”

― Chuck Palahniuk, Fight Club

 

The older I get, the truer this seems. 

[Ralph]

We got rid of most of our stuff a few years when we moved into a small flat for the build. I found it very freeing. We're about to move into 150m2 for just the two of us and I'm determined not gather more crap.

[TerryE]

As @Iceverge says, I have a reasonably large stone clad "cottage style" build to passive standards.  As I said recently to @shuff27 when showing him the build, I can't think of any things that I'd tweak if we were doing this over let alone fundamentally change.  Have a look at my blog.  

[jack]

21 hours ago, MLR1907 said:

... but the other half worries about running out of hot water and cold floors if the heating doesn’t need to be on much! 

 

If the heating isn't on, it's because the house is currently warm enough. If the house is warm enough, then the floors won't be cold! 

 

As a point of comparison, we have a 4 bedroom house just shy of 290m²,  with passivhaus levels of insulation and airtightness, and MVHR. We have concrete floors throughout the ground floor, except for the TV room. The floor remains a pleasant continuous temperature no matter what the weather is like outside. 

As for running out of hot water, put in a big enough tank and you never will. If you run a lot of showers, I'd also suggest getting a waste water heat recovery unit. We only have a 250 litre unvented cylinder heated to 50 deg C by a 5kW ASHP, but we very rarely run out of hot water, even with two teenagers in the house. It happened for the first time in months the other day, when all four of us had showers in quick succession and one of the kids was in there singing away for god knows how long before we realised the water was still running!

[Faz]

There is 'green' and there is what you actually want - I was going to install a gshp - we have a 1/2 acre plot.  The drawings came back and they intended to cover every square inch with the ground loop - no trees or bushes in our garden then!  I binned the concept and dashed to gas! It is not going to need much heating tbh so f*ck it.

 

Instructed Solarcrest for the MHRV though - they have done one for us before and I can't fault them.

[MLR1907]

Thanks all, good starting advice. I’m looking at SIP’s for the build, and very much passivhaus standards in terms of being “green” rather than just fitting LED lighting and water saving appliances! 

 

9 hours ago, Faz said:

  I binned the concept and dashed to gas!

 

I think I’ve already decided that given the spec of the house I’m hoping to achieve, GSHP would be a waste of initial outlay,  (but can you really not plant a bush or tree above the pipes??) 

I’m hoping I can be convinced that ASHP can do what I want efficiently.  I understand the convenience and minimal cost of it but I really don’t want to install gas. It’s one service I wouldn’t need to pay for install, the government are scrapping it from new builds in that not too far future, and I’d like our energy to be from renewables. I plan on solar PV on the roof and already use a supplier that is 100% renewables. Yes my gas is currently carbon offset but if I can ditch it’s use altogether, then that’s better for me. 

 

19 hours ago, Iceverge said:

In my opinion 30-40m2 per person is generous living space.

 

My current cottage is tiny (not sure exactly of the top of my head), and it suits me (despite having to keep a lot of my tools and equipment in a storage unit miles away) but it’s not how I would like to being up my children if I can afford not to. I’ve got each of the rooms down to what I think is the smallest they can be comfortably, I don’t see the point in self building if I’m going to compromise to such an extent where I cramp things in and force the kids to share rooms growing up. I may as well buy something already built and save myself the hassle and work! Although, if when I get to the point of showing my drawings to an architect he can show me a way of shuffling to save space then I would of course be open to it. 

We need a workshop as we often work from home (one of us will be full time once we have children) so included in my estimate of size is a garage and a workshop along with a disabled accessible guest room with en-suite for the MIL who may well become a permanent resident. 
 

I guess my point is, I’m building for the future and don’t wish to grow out of the house, I plan on building green also in the sense of sourcing locally, choosing materials wisely etc to minimise impact there. 
 

Does anyone have a good source of information on the different types of foundations? I know the plot etc will affect what can be used but I’d like to understand all the different options.

[Iceverge]

1 hour ago, MLR1907 said:

We need a workshop as we often work from home (one of us will be full time once we have children) so included in my estimate of size is a garage and a workshop along with a disabled accessible guest room with en-suite for the MIL who may well become a permanent resident. 

 

This changes the balance significantly!

 

Best of luck. 

 

As for green building. Minimise your energy demand. Build your house out of things that were recently plants. Heat it with renewable electricity. 

 

Use an insulated raft foundation like isoquick or kore. Minimum use of concrete and thermally excellent. 

 

[Bitpipe]

I echo all the good advice above, avoid 'greenwash' and the implication that a low energy house (I'd like to ban the word 'eco' - a Grand Designs disease) imposes a lifestyle on the occupants.

 

MVHR is a good example - provides energy efficient ventilation to your otherwise airtight home by harvesting the heat that would otherwise leave with the stale air being extracted. Some people  extrapolate this to 'you can't open a window in summer'.

 

Of course you can, winter too if you like. Our slider was open for hours yesterday as the dog pinged in and out.

 

Invest in good fabric design and attention to detail when building. Treat the house as a system, not a set of unconnected functions (e.g. heating, DHW supply, ventilation etc.). Pay as much attention to summer overheating as you do to winter cold.

 

You can spend money on capturing waste heat from your shower, use rain water to flush the loos and even try and recycle your grey water but you quickly enter the world of diminishing returns where you spend much more than you will ever recover in benefit.

[TerryE]

We much +1 to @Bitpipe's comments.  MVHR gives you lots of fresh air in the colder months without having to throw heat out of open windows or trickle vents.  Brilliant -- but that doesn't stop us opening windows when it is warm enough.  IMO, the only good argument for not doing this is if one or more of the occupants is allergic to pollens etc.

 

You really need to think of the house as a system and understand where your relative thermal gains and losses are.  IMO, the PH and SAP spreadsheets are just too complex to do these sorts of trade-offs.  The sort of simple spreadsheet that Jeremy Harris or I developed is plenty detailed enough.  

 

The whole build process is one of trust(-ish) but validate and verify at every step.  You need to understand potential thermal bridges and make sure to avoid them when practical.  You need to be sympathetic to the fact that UK building trades in general have little or no understanding of the importance of the detailing needed to get good thermal performance, but this doesn't excuse sloppy workmanship.   You either (i) need to pay the premium for a subcontractor that does have this understanding; (ii) validate and specify at every step, or (iii) accept that you will be disappointed with the as-built performance of your house.

[MLR1907]

Thanks @TerryE. All solid advice, confirming what I was getting hints of from other research. Thank you also for your blog,  I've just started browsing and it is a mine of good information.  We are in no rush to do this build, it's very much a learning project for me (I always need something to keep me busy) it's about getting it right rather than getting it fast.

 

Could you possibly point me in the direction of the spreadsheets you mention?

 

Thanks

[Pete]

2 hours ago, MLR1907 said:

Thanks @TerryE. All solid advice, confirming what I was getting hints of from other research. Thank you also for your blog,  I've just started browsing and it is a mine of good information.  We are in no rush to do this build, it's very much a learning project for me (I always need something to keep me busy) it's about getting it right rather than getting it fast.

 

Could you possibly point me in the direction of the spreadsheets you mention?

 

Thanks

We built to Passive standards but never tweaked the house design. Our house is 330m2 and has a lot of glazing which is not compatible with Passive!! 

We kept things really simple in terms of ufh and it is all one zone. We use ASHP for ufh and hw and it works well for us. We only moved in two months ago so we are still getting used to the ASHP and tweaking it but our electric bill for last month was £122. The house does not have any other form of heating and the stat is set at 21. 

We built in t/f and used the Passive frame/foundation combo. As @jacksays the floors are always warm if the house is warm. We just used the concrete slab as a thermal store and it is brilliant. We only have porcelain tiles so it is great at heat transfer. 

Mvhr is a must and the fresh air feeling is lovely inside all the time.

[joe90]

1 minute ago, Pete said:

We built to Passive standards but never tweaked the house design. Our house is 330m2 and has a lot of glazing which is not compatible with Passive!! 

We kept things really simple in terms of ufh and it is all one zone. We use ASHP for ufh and hw and it works well for us. We only moved in two months ago so we are still getting used to the ASHP and tweaking it but our electric bill for last month was £122. The house does not have any other form of heating and the stat is set at 21. 

We built in t/f and used the Passive frame/foundation combo. As @jacksays the floors are always warm if the house is warm. We just used the concrete slab as a thermal store and it is brilliant. We only have porcelain tiles so it is great at heat transfer. 

Mvhr is a must and the fresh air feeling is lovely inside all the time.

+1, I did similar, kept things simple, one zone, ASHP, MVHR etc etc and like Pete it all works very well.

[TerryE]

Re UFH, you need to distinguish loops vs zones.  Keep your individual loops as close to the same length as possible and < 100m.  So we have 3 × ~100m loops (IIRC the shortest is 92m)  all drawn off a 300m coil.  4 × 75m could have worked as well.  Don't have any joins in your UF pipework below slab.  The reason for the suggested 100m max is the head needed to get the necessary flow.   I used the delta T across each zone to trim the flow rates and balance them, but once balanced, like @joe90 and @Pete, I run my 3 loops as a single zone.  There's little point in doing anything else in a passive-class house, IMO.  Ditto no point is trying to dick around with time-of-day temperature strategies. 

 

In terms of JSH's spreadsheet, the obvious Google search gave it as the 1st hit: Fabric and Ventilation Heat Loss Calculator,  though IMO, you could dump most of the complexity about the under-slab soil temperature as it is going to be a pretty constant 12-14 °C for most UK insulated slabs that are in direct contact with the soil.  Ventilated are another issue.

 

Yup KISS -  Keep it Simple Stupid.  

[Dave Jones]

all depends on if you will be staying in the house long term or selling.  If selling don't go eco £££££ crazy you wont get a return out of it. Money better spent on tangebale items, kitchens, bathrooms, doors etc will get you more bang for your ££

[TerryE]

On 05/03/2021 at 19:13, Dave Jones said:

If selling don't go eco £££££ crazy

 

Ah, the tragedy of the commons. 

 

It seems to me that there are two broad classes of self-builder (i) those you are using their personal efforts to maximise the house they can get for a cash constrained investment; (ii) those who are self-building primarily because they don't like the pre-built choices on offer and want to have design control over the house they want to live in. Whereas the first category might want to repeat (and improve) the experience, the second will tend to want to make the most of their "dream house" and so will have different payback trade-offs to make.

 

In our case, we wanted a warm, cheap to run, pretty much zero maintenance house that would last us through our "3rd age" (as the French call it).  BTW, in our experience designing for energy efficiency didn't add materially to the build cost.  The big premium was as a result of LPA imposed aspects like using locally quarried hand dressed stone for the skin and a slate roof because they wanted the house to fit well in the local context in the village (mostly 1700s and 1800s stone houses).  However the fact that our plot was a "freebie" calved from our previous large garden more than compensated for this and the result was a fine looking house that is a pleasure to live in.