Practice Cabin

[markocosic]

Hello,

 

 

An Englishman with a Lithuanian wife here; building a "practice cabin" on some land she bought at auction whilst there was nothing else to do...

 

There's a saying here (Lithuania) that the first house you build is for your enemy, he second is for sale, and the third is for yourself.

 

 

As such:

 

 

House 1:

Bought an house that wasn't new. Fixed it up to the point that most of the population would think it great. Annoyed by various bits of it. Longer term We'll build in the back garden then sell the original house.

 

 

1970s ex local authority 2 bed terrace in Cambridge.

 

Previous +1 owner was a handy andy carol smiley type. Wiring bodged. Plumbing bodged. Heating bodged. Porch bodged on the front. Attic converted by knocking out all the trusses and calling it good etc. Time (20+ years) says it wasn't going to fall down but flooding or fire were reasonably likely. I think my favourite was the cooker gas supply "sealed" by showing some tile adhesive in the end, bashing the end of the pipe flat and folding it over, then slapping some tiles over it. 

 

Stripped back to brick and joists internally; chimney removed down and joists replaced; french windows and larger kitchen window to rear elevation; ground floor open planned; roof jacked back up and steel purlins added; structural partitions on 1st floor to support attic floor. (i.e. sufficiently unbodged not to fall down)

 

Re-wired, re-plumbed, insulated where practical mainly to reduce cold spots/for comfort rather than energy (450 mm loft rolls to the eaves; cut back the brick cavity closures and celotex-ed; 9 mm plasterboard with 25 mm foam to existing concrete window headers; 30 mm EPS between battens on existing ground subfloor w/18 mm chipboard and 14 mm engineered oak on top), MVHR to 1st floor bathroom/bedrooms (for forced ventilation - bedrooms are small, I take in lodgers so doors are shut, the house nowhere near airtight enough for MEV to work, and open windows are a poorly controlled)

 

Biggest wins: MVHR is astounding; if switched on I wake up comfortable; if off I'll wake with did-i-eat-a-hamster throat from mouth-breathing at night due to high CO2 and the windows are moist with condensation. A little mini-split downstairs that bought during a fit of heat induced insomnia/rage is worth every penny for the week or two each year when it's >30C during the day and >25C at night. Works well for heating (the whole house) in the shoulder seasons too.

 

Biggest frustration: mortgage providers won't let you knock down these pieces of rubbish and rebuild them; working around existing rubbish takes far longer, costs more, and achieves a worse result than starting from scratch; tradesmen serving the resi sector are in short supply, with far too many arrogant idiots that need as much supervision as children and come with 10x the back chat.

 

Biggest regret: buying cheap double glazed doors and windows with the structural integrity of wet spaghetti and the airtightness of colander; not digging out the subfloor and throwing in an insulated one with UFH; not planning ahead for a mini-split A/C and running lines to the upstairs landing. (cold air falls / warm air rises so if it's cool bedrooms you're after then you really want that indoor unit on the upstairs landing)

 

 

House 2:

The practice cabin near Moletai (Lithuania). She bought some land at auction and we're building a timber frame "cabin" (12x6m and 1.5 storey/warm roof) as a practice run for building a timber frame house (~6x6m and 1.75 storey/warm roof) in the back garden in Cambridge.

 

 

SWMBO bought 1 hectare between the highway and some high voltage power lines. It's prettier than it sounds (has trees and the region is just outside a national park) and crucially wasn't zoned as forest or national park. (she's 6' for some context on meadow/weed height!)

 

 

 

Planning wise...if <80m2, <8.5m tall, and <6.5m wide, and not a principal residence...and not in the forest or national park...knock yourself out. 

 

Building regs...really quite tough if you'd like a resi building. The paperwork is the same for a single house as it is for an apartment building. GPS survey, aerial photo, soil survey, foundation design, structural design, energy modelling, drainage design, electrical design, you name it at €500-1,000 apiece. There isn't really the equivalent of a "deemed to comply" detail and it's the government that set the standards for things not falling on your head rather than the lenders setting the standards for things that won't fall on your head during the mortgage period.

 

For an energy perspective:

 

U-Values:

Wall 0.1

Roof 0.08

Windows 0.7

 

+MVHR

+RES (i.e. PV) to offset "most" of the energy consumption of the building

 

https://epbd-ca.eu/ca-outcomes/outcomes-2015-2018/book-2018/countries/lithuania

 

Personally I think this is a step too far. The A+ is ok. (eminently doable and cheap) A++ is getting silly. (probably viable for mid rise apartment buildings with a flat roof full of PV; but frankly you'd be better off spending that money on public renewables that generate in winter when that energy is actually needed)

 

 

Building regs...if you'd like a non-resi building (a house <80 m2; i.e. a summerhouse / cabin)...are essentially zero though. So we're aiming for:

 

A 12x6 metre "barn" style cabin on screw foundations (I dislike concrete and with no access road / the frost line here being a metre you'd need epic quantities); a variation on Swedish platform framing (sheathed internally with taped OSB as the air tight / vapour retarder layer; rather than solid PE); with posts/ridge beam/warm roof (not that I'd ever add a slightly cheeky mezzanine after it had been certified at 72 m^2 you understand); and insulation with mineral wool (cellulose requires trusting somebody else; fibreglass just falls to the bottom of any cavity and the mice love it; and for foam...you'd best like mice)

 

http://blog.lamidesign.com/p/swedish-platform-framing-info.html

https://www.paroc.com/applications/building-insulation/walls/timber-frame-walls

 

Target U-Values:

Wall 0.13 (paroc nordic wall = 25 double plasterbaord+50/45 insulated service+12 OSB+200/195 stud+50/45 overlay)

Roof 0.1 (same as the wall but 250/245mm rafter and less bridging)

Floor 0.1 (22 OSB+250/245 joist full fill+6 OSB+100 underlay)

Windows nominal 0.7 (rehau euro 70 3g)

 

Cladding (walls AND roof) to be vertical board on board in black in this style:

 

 

 

This is where we're at:

 

 

 

Plenty still to do. Joined to ask about air tightness testing techniques (the framers are contracted to get the shell up to the level of wind membrane on the outside, and the OSB on the inside, then it's up to us to do final taping/testing of that inside layer; fit doors/windows; do the external cladding; all the internal fit out)

 

 

Services wise:

 

Hot water and bathroom UFH / towel rail from a from GSHP (SWMBO thinks solar is ugly; I think air source units are noisy / fugly but mainly I would like to experiment with a GSHP / picked up a Danfoss DHP-H 6 with 1,000 run hours for £650 ).

 

Will install an MVHR unit and bought one but got screwed over by Brookvent (refusing to supply spares for a 4-year old MVHR unit with a failed fan).

 

Need to learn about aerobic sewage treatment plans and drain fields. Need to learn about land drainage. First need to get to a box weather tight enough to breathe and relax some without worrying about how drawings might get mis-interpreted next...

 

 

 

[markc]

Hello and welcome, looks like a fantastic project

[SteamyTea]

Welcome.

I think you will be teaching us more.

 

Regarding air testing, you can make up your own unit with a car radiator fan, a speed controller, a clear water pipe and a calculator.

 

Are you going with a borehole for the GSHP?

 

 

Edited April 12, 2021 by SteamyTea

[jack]

Congrats on the best introductory post I've seen in a while!

 

2 hours ago, markocosic said:

Will install an MVHR unit and bought one but got screwed over by Brookvent (refusing to supply spares for a 4-year old MVHR unit with a failed fan).

 

I'd be really surprised if you can't slot in an identical motor from another manufacturer. It's surprising how much of the components these things share. I think I read something like 80% of the market uses exactly the same plastic heat exchanger, for example.

 

If you still have the unit and are interested in following up on this, post some details in the MVHR sub-forum. I'd be surprised if someone can't help you with some clues about a potential replacement.

 

[joe90]

1 hour ago, markocosic said:

I think air source units are noisy / fugly but mainly I would like to experiment with a GSHP

Welcome, wow what a project (jealous emoji). From my reading the GSHP gubbins is noisy and indoors whereas ASHP are outdoors and can have ventilated cladding to reduce the already  low noise level.

[jack]

3 minutes ago, joe90 said:

From my reading the GSHP gubbins is noisy and indoors ...

 

I could be wrong, but I think that info came from a single poster (I believe I remember who, but won't say in case I'm wrong). I actually think it's more usual for the GSHP unit (the heat pump itself) to be placed outside the house. Since it doesn't need a high volume airflow like an ASHP, there's also nothing to stop it being enclosed in a relatively sound-insulated enclosure.

 

I think the main issue for the low interest in GSHPs is relative cost. It costs to dig, then you need to buy loads of pipework, then you need to buy the anti-freeze that fills the pipes. The anti-freeze then needs to be replaced every few years, from memory, which adds more cost, along with the hassle of safe disposal of the old fluids.

 

For all this cost an effort you get a slight improvement in COP relative to an ASHP. The additional costs of GSHP mean you'll probably never make up the higher installation and maintenance costs.

[markocosic]

All of the above SteamyTea ?

 

 

Brookvent...will post and ask. 

 

 

GSHP...

 

...the base plan was a €1000 mini-split for space heating/cooing and an immersion cylinder. (there'll also be a wood burner for those days that are cold enough to warrant lighting it without risking immediate overheating)

 

 

...the experiment is the GSHP. Winter drops to -20C worst case so potable water stays indoors. For these GHSPs with built in hot water tanks you kinda have to put them indoors:

https://assets.danfoss.com/documents/52352/BC006686463914en-010901.pdf

 

I'd like to see how noisy these really are. And what the run hours to serve a DHW load (2 hr runtime?) and space heat load (naff all from and cycling a couple of times a day into a decent buffer tank?) are. Ground loops will be trenched as there is plenty of land that needs draining better via ditches and a digger is cheap vs a drilling rig. (we already have the bill for a 55 metre potable water borehole...no thanks to more of that)

 

If too noisy it'll either get reverted to a glorified 4.5 kW immersion only unit (the original plan for DHW) with option to boost by 6kW if required; or moved into an outdoor shed built over the potable water borehole. (that wouldn't have windows and would need lots of insulation and probably heating but it wouldn't be a bad thing to keep the borehole head warm)

 

These were spendy affairs when new and dear lord does it weigh enough (200 kg empty / 400 kg with water in) so I'm hoping that it's not as noisy as a those basic Kensa units sat on top of some loose floorboards in the airing cupboard between all the bedrooms made of single layer tissue paper partitions where it needs to run for hours to meet a high space heat load etc. I'm not too precious about it given the cost to experiment here (probably £1.5-£2k all in) vs on the final build. 

 

 

Folks do use ASHPs here. Dry winter and high enough off the ground for snow. Monoblocs need antifreeze in the system. All of them need external pan heaters to keep the oil/refrigerant in the compressor in the right place which is not ideal for occasional use. All of them are noisy (I have one on the first house) which spoils the outdoors and all of them need maintenance (twice a year clean) so I wouldn't want one of these again. Cheap; effective; but less than ideal.

[SteamyTea]

I think some of the problem with internal GSHPs is that there is solid pipe between the pump and the manifold. A Kensa install I looked at had flexibles fitted. While you could hear it when standing next to it, was silent once one was outside the plant room.

 

Are these noisy ASHPs old ones that are non inverting types?

It used as bike stands?

[markocosic]

Brand new Panasonic Etherea inverter.

 

Noisy AF before being dismantled and lousy insulation secured. Noisy afterwards. Not as noisy as children with windows open. But audible from about 3 doors down and the noisiest thing in the neighbourhood if operated at night.

 

Fine in rural areas with screening / vegetation and no neighbours but I wouldn't want one on a city plot that you're trying to keep quiet. Bloody effective in heating mode during the shoulder season too (3.4 kW @ -7C but more like 5 kW+ >7C; soon reheats air in a modest building even if walls are cold...but you need higher setpoint for an equivalent thermal comfort due to all that air movement; say 23C on a mini split air handler equivalent to 20C on radiators). Absolute bliss when it's silly hot outside. ?

 

 

50 dB(A) is more offensive in person than on video. They high level wall mount then measuring the sound 0.8 metres below the unit for the brochure - real world will be noisier.

 

https://www.saturnsales.co.uk/images/products/editor/CS-Z_Range.pdf

 

 

That DHP-H 6 GSHP unit is nominal rated at 41 dB(A) and as a fixie (rather than inverter that varies its speed) I suspect it's easier to isolate the vibrations as they're at a set speed. Compressor sits on an isolating frame within the GSHP unit; 400 kg (full) GSHP unit sits on isolating feet (and that 200 kg of water as an integral part of the 100+ kg GSHP frame  vs <20 kg compressor and frame helps with vibrations); flexible sold pipe connections withn GSHP unit from isolating frame to main body; flexis from main body to building pipework. We will probably enclose it. See what happens though - it's an experiment. 

 

My benchmark is an A+++ siemens fridge/freezer at 39 dB(A)...allegedly...when it's in the special "Volkswagen mode" for cheating the efficiency and no doubt noise tests rather than in regular operation and not counting door openings. Else definitely noisier.

 

And a Vaillant Ecotec 824 combi at 46 dB(A)...which must be in some steady state mode rather than DHW production or the whirring it makes on startup / purging.

 

 

Etherea noises (excuse unfinished mess background)

 

 

 

 

Edited April 12, 2021 by markocosic

[markocosic]

Apparently 47-52 dB(A) for the shoebox units - a bit louder than a combi / more like a dishwasher:

 

https://www.kensaheatpumps.com/shoebox-ground-source-heat-pump/#Product-technical