Attempting a straw bale, off-grid passive house in Somerset

[SteamyTea]

8 hours ago, Smallholder said:

As for air tightness, there are at least a few PH spec strawbale houses in the UK, so it's certainly possible.

Is that when using straw bales as the structure, not just the insulation?

8 hours ago, Dan F said:

but unless you are aiming for PH Plus or Premium this is complelty non-consequential.

Right, I had forgotten that there were higher PH standards.

7 hours ago, Smallholder said:

gives me an estimate of £21,575.50

Less than many spend on a kitchen or bathroom.

7 hours ago, Marvin said:

Is that a quote from Yes Prime Minister?

No, my first boss.

[gc100]

9 hours ago, Smallholder said:

I've been working with a very knowledgeable chap locally, who has created modelling software to help with this.
Using downloaded solar intensity data, hour by hour over the course of a whole year, we are able to calculate how much the array should produce every hour. We then compared this back to a local solar array of 4kw, plugging in the specs of this array to make sure it is accurate, which it was.

Then we add battery storage (I'm thinking I'll start with 28kWh, it's modular so we can add more if needed. About £850 per 3.5kWh unit) information, and the software gives us an hour by hour battery capacity. When it reaches 100%, further solar generation is ignored, until the battery capacity dips below 100%.

This then shows the instances over the course of a year, when the batteries run down to zero. This modelling includes a small wind turbine, that helps as it runs at night and slightly more during the winter.
It sounds counter intuitive, but it may well be environmentally wise to run a small diesel generator for those few occasions each year, rather than investing in more and more PV and batteries. These, of course have a carbon footprint like everything else.

 

We already have an EV, which we charge at home, but also at the farm where I have already set up a small (2.25kW) solar array with small (7kWh) battery storage.

 

We've modelled home electrical consumption based on best guesses.

In winter, if possible I plan to use a biomass boiler for DHW and underfloor, which will take load off the electrical system

Could you give me more information on this battery storage you are planning to use? I would like to get some for my solar but it’s not adding up currently but that seems ‘cheap’ 

[Smallholder]

2 hours ago, gc100 said:

Could you give me more information on this battery storage you are planning to use? I would like to get some for my solar but it’s not adding up currently but that seems ‘cheap’ 

 

When I built the solar setup for the barn, I had a good look at battery options and ended up going with Pylontech US3000 batteries.
These I got for under a grand each (48v, 3.5kWh capacity and 90% D.O.D), and they can be daisy chained up to a max of 8 units, without any need for additional hardware.

I initially got one battery, then added a second about 6 months later.

There was a lot I had to learn to create this fairly small and simple set up. One example, was that each battery has a max current that it can take in terms of charging/discahrging.
So if you are looking to take a relatively high load out through an inverter, you may need more batteries so that the load you're taking can be split across these batteries.

See image attached.

Edited November 4, 2021 by Smallholder

[Smallholder]

3 hours ago, SteamyTea said:

Is that when using straw bales as the structure, not just the insulation?

Right, I had forgotten that there were higher PH standards.

Less than many spend on a kitchen or bathroom.

No, my first boss.

 

My understanding is that it's easier to achieve PH when using the bales as the structure, as in this case they are far more compacted and therefore more air tight.

There are examples in the UK of load bearing PH, and timber framed PH with straw bale walls. The builder of the latter said it would have been easier with load bearing technique.

https://passivehouseplus.ie/magazine/new-build/norfolk-straw-bale-cottage-aims-for-passive

 

I get it, people spend a lot on kitchens & bathrooms, but that doesn't necessarily mean they'd be happy with spending the same money again for an additional (optional) part of the project.

I'm keen to have renewables, and storage anyway, so that for me is an inescapable cost. Then when given the choice to spend £20k or more to also get a grid connection, or to maybe spend half that to get more generation or storage, I'd prefer the latter.
But I also make the decision with my eyes open. Maybe it means we'll have to be careful with electrical consumption on occasion during the winter. I accept that.

[SteamyTea]

1 minute ago, Smallholder said:

 

I'm keen to have renewables, and storage anyway

So is the national Grid. We are close to 50% RE now, and we get that very reliably for 20p/kWh, with no large upfront cost, and no replace costs.

 

I do understand the charm of energy self sufficiency, but the huge upfront, and maintenance costs are off putting.

Even with my low energy usage <5 MWh per year, it is not worth me swapping out my storage heaters for a wet ASHP. A2A is marginal.

I keep meaning to look at just fitting PV to heat my water.

If I had a bigger house, the whole thing would be easier, but with a 4m by 8m footprint, and the half the roof being SW facing, options are limited.

[Smallholder]

3 minutes ago, SteamyTea said:

So is the national Grid. We are close to 50% RE now, and we get that very reliably for 20p/kWh, with no large upfront cost, and no replace costs.

 

I do understand the charm of energy self sufficiency, but the huge upfront, and maintenance costs are off putting.

Even with my low energy usage <5 MWh per year, it is not worth me swapping out my storage heaters for a wet ASHP. A2A is marginal.

I keep meaning to look at just fitting PV to heat my water.

If I had a bigger house, the whole thing would be easier, but with a 4m by 8m footprint, and the half the roof being SW facing, options are limited.

True, the national grid is getting greener, but is still less than 50% clean.

If you are grid connected, then you're right, it's an easy way to get clean-ish energy without a large upfront cost. But we are not grid connected, so the cheapest option is the £20k plus of getting grid connected, and even then the energy isn't yet all that clean.

 

There are two separate factors here, which are money and carbon. Sometimes they push in the same direction, and sometimes they conflict.

[SteamyTea]

58 minutes ago, Smallholder said:

There are two separate factors here, which are money and carbon

Yes, this is always the problem, and we are still, on electricity, paying a premium for installing new RE, but the gas network is not contributing much to it.

For twenty years everyone has known that a carbon tax is the way to go, but each government has be too scared to introduce it, so they have this sneaky tax what most people do not realise.

A 1p/kWh would have raised around £16.5bn in 2019.

Dirt cheap.

[Delbot]

Hi, we are in Mid Devon and recently got planning for an offgrid strawbale house near Cullompton. The planning took 14 months to get.

We had a very good planning consultant and support from a local councillor who took our application to the commitee for consideration after the planning officer refused it. 

We purposely did not go down the paragraph 79 route as we were told it was very expensive and time consuming.

Our build sounds very similar to yours, only 3 bed though.

The main thing I am having difficulty with at the moment is the cement free foundations, I have worked on car tyre foundations before, very labour intensive.

Friends in Castle Cary built their straw house on Gabions filled with stone.What are your plans?

I'd be very interested to compare notes.

All the best with your project.

 

[Smallholder]

Delbot that's great news! Congratulations. I bet's it's been quite a journey.

At the stage we are at right now (applying for planning imminently) we're not yet thinking too hard about foundations, but my initial thought was that we'd go the gabion route. It feels strong, and the kind of construction we could do ourselves. 
I have chatted a few times to Matt at Wellspring Architecture (he worked under Barbara Jones for several years, and seems to be a UK authority on straw bale construction?), who I think we'll work with in some capacity if we get planning. I figured we'd have this discussion with him if and when we get approval.

 

I'd be very interested to meet up with you and learn a bit more about your project, if you're happy to do so? Also Castle Cary is only a few miles from us, and I'd be keen to see what they have done there.

 

In terms of our project, we have the building design fully finished now, and a landscape architect is working on their bit.

We have a concept design for the WETs system that will 'process' our black and grey waste.

The next step is to pull all this work together, and present to the Design Review Panel, which we're ideally hoping to do in roughly 4 weeks. Then see what they come back with.

 

We'd have loved to opt for a simpler planning application process, but our farm is in open countryside, and getting planning here is far from straightforward.

 

The very best of luck with your build.

[Smallholder]

Quick update.

 

We have our Design Review Panel meeting this morning.

 

Fingers crossed.

[markc]

1 minute ago, Smallholder said:

Quick update.

 

We have our Design Review Panel meeting this morning.

 

Fingers crossed.

Good luck 🤞 

[George]

I'd missed this thread before now. 

Structural engineer questions...

 

Are you going for a load bearing straw bale wall or a timber frame with a straw bale infill? 

Are you doing a stonework plinth with a suspended floor?

Have you done a ground investigation? On site clay plaster may be an option and while it is labour intensive, it does cut down massively on import (useful if you need to shift a bit of mud from landscaping)

Are you doing drained rubble fill foundations or some sort of raft? 

 

As I'm a part time farmer and structural engineer I've always been very interested by straw bales. We still make a few little bales but nowhere near as many as we used to. While I've done a few concepts proposals for straw bale homes they've never made it to construction.

[LSB]

On 28/10/2021 at 22:20, ProDave said:

I have only worked on one straw bale house.  I seem to recall part of the issue sourcing bales, apart from the size issue, was moisture content which seemed a lot more important for something that will be stacked up and kept for many 10s of years than normal bales that will usually be used within a year.

 

It was a case of needing perfect weather conditions leading up to harvest and then between harvest and baling.

This year would have been fantastic in the East.

I do have a contact that does straw bales - small or large and despite where we are he will ship, he sends hay and potatoes to Somerset.

 

hadn't read the whole post when I put this and now realise that this is sorted

 

Good luck with the Design Review, look forward to hearing about it.

 

Edited September 9, 2022 by LSB