Owner-Builder looking to build our family home!

[joe90]

15 minutes ago, SteamyTea said:

Why we should use large diameter pipe for MVHR,

I discounted using larger pipe due to its inflexibility and not being able to feed the pipe through holes between joists 🤔

[AccidentalSkydiver]

48 minutes ago, joe90 said:

I discounted using larger pipe due to its inflexibility and not being able to feed the pipe through holes between joists 🤔

I know lots of American homes run like HUGE insulated piping, but their homes are usually huge to boot- think 75mm radial is standard here isn't it? planned on the MHVR going in the utility at the back of the workshop with the boiler and media closet... can't be a techie without a house full of tech 😁 this would give us direct access to the ground floor through the wall to the living space and then also to the WC/utility space

Edited March 17, 2022 by AccidentalSkydiver

[SteamyTea]

1 hour ago, joe90 said:

I discounted using larger pipe due to its inflexibility and not being able to feed the pipe through holes between joists

That is why initial design is so important.

Heating, plumbing, MVHR and wiring are often considered second, and you can tell because the design and positioning is often compromised.

[joe90]

29 minutes ago, AccidentalSkydiver said:

I know lots of American homes run like HUGE insulated piping,

Usually for warm air heating which needs a lot of air. I also ran all water pipework in plastic (I am a late convert from copper), dead easy to feed through without loads of sharp bends and joins.

 

[joe90]

2 minutes ago, SteamyTea said:

That is why initial design is so important.

I agree BUT, you still cannot feed a stiff (non flexible)  pipe through holes in joists. My 110mm drainage pipe had to be installed as the i joists were installed, sooo much easier to use flexible pipe wherever possible.

[SteamyTea]

3 minutes ago, joe90 said:

I agree BUT, you still cannot feed a stiff (non flexible)  pipe through holes in joists. My 110mm drainage pipe had to be installed as the i joists were installed, sooo much easier to use flexible pipe wherever possible.

You have kind of argues against yourself there.

Take my house.  It has 1 internal stud wall downstairs, and three upstairs.  For the sake of moving the downstairs wall 125mm, there would have been a clear drop from the loft to the ground floor.  All the bathroom pipework could have been fitted into that.

As it is, there is a waste pipe boxed in, in the living room, no sockets on one wall (both sides), really a master class in how not to do it.

[joe90]

8 minutes ago, SteamyTea said:

You have kind of argues against yourself there.

I disagree

8 minutes ago, SteamyTea said:

For the sake of moving the downstairs wall 125mm, there would have been a clear drop from the loft to the ground floor.  All the bathroom pipework could have been fitted into that.

Yes, a good example of bad planning but here we are talking about ceiling joists, how are you going to feed non flexible larger diameter MVHR pipes through ceiling joists without leaving a hole in an outside wall 🤷‍♂️  (My I joists allowed 100mm max holes in them and not near the ends.). I used my first floor airing cupboard as a riser to the loft which houses the MVHR.

Edited March 17, 2022 by joe90

[SteamyTea]

5 minutes ago, joe90 said:

I used my first floor airing cupboard as a riser to the loft which houses the MVHR.

By designing in more features like that if you can.

[TerryE]

In terms of cost and simplicity using a distribution manifold and standard flexible ducting as @joe90 shows above is far more straightforward and easier to balance.  Ours is pretty much the same as his and @ProDave have shown.  We doubled up on 3 vents in our house: the LR inlet; and the inlet and outlet in our kitchen / dining room, because the required flow rate was higher that we could achieve with a single pipe when balancing the system: you can only throttle back an individual terminal manifold.

Edited March 17, 2022 by TerryE

[Simplysimon]

On 15/03/2022 at 16:50, AccidentalSkydiver said:

He has already agreed with me 2x6 with a 600mm OC, california corners at all external corners

 

for what? strength or insulation, strength yes, insulation just about adequate.

 

 

[AccidentalSkydiver]

14 hours ago, Simplysimon said:

 

for what? strength or insulation, strength yes, insulation just about adequate.

 

 

Strength, I've solely been focusing on the structural design. At the moment, the design has been my number one key point, calculating dead loads - material amounts etc. However I did some research into average cold-zone temperatures and the standard for insulating values in those areas such as Wainright AK. The US IRC 2015 standard for insulation the walls in Arctic Slope region (Alaska) is R35^[1] - No where in the Midlands is going to see average temperatures of -29c for prolonged periods of time (Its currently -27c as we speak). According to Rockwools website^[2] if you ran 2x6 at 600mm OC, to achieve a U0.028 / R35.7 you'd need to run 5.5in (140mm) then an additional 5in (130mm) outside your 9mm sheathing + vapour barrier + then your brick ties, air gap and masonry rain screen. 

My original plan was to fill the 2x6 with 145mm insulation batt, 18mm sheathing and then 145mm - but further reading has shown (IMPO) that I could easily drop to a 2x6 145mm batt + the external 50-100mm, with good air sealing details and still achieve the a good insulation level without being excessive. - I have been reading through the idea of a larsen truss (which my dad called a "double stud, single strength wall" for what thats worth) to encapsulate that extra layer of insulation between the rain screen and the actual interior frame and reduce breaks in the sheathing / vapour barriers.

Sources and reading material
^[1] https://www.ahfc.us/iceimages/manuals/building_manual_ch_02_special_considerations.pdf Table 1 Thermal envalope (Page 6)
^[2] https://bim.rockwool.com/rvalue/

Further info

https://extensionpublications.unl.edu/assets/pdf/g2233.pdf
http://cchrc.org/media/ArcticWallReport.pdf

[TerryE]

Our Larson strut cassettes were assembled in factory on assembly jigs.  Too much of a PITA making these up on site, IMO

[Simplysimon]

7 hours ago, AccidentalSkydiver said:

I could easily drop to a 2x6 145mm batt + the external 50-100mm,

so why not go a 245-300mm i beam wall and build onsite?

 

[Iceverge]

 

 

Here's a pic of my favourite stick build as described previously. 

 

Cellulose, continuous external 22mm woodfiber insulation , robust osb airtightness layer, windtight by design, everything nailgun compatible, off the shelf timber sizes, generous service cavity, negative embodied energy, excellent decrement delay, completely moisture safe, U value 0.13 W/m2K. 

 

Yum Yum Yum! 

 

[AccidentalSkydiver]

On 20/03/2022 at 01:31, Iceverge said:

 

 

Here's a pic of my favourite stick build as described previously. 

 

Cellulose, continuous external 22mm woodfiber insulation , robust osb airtightness layer, windtight by design, everything nailgun compatible, off the shelf timber sizes, generous service cavity, negative embodied energy, excellent decrement delay, completely moisture safe, U value 0.13 W/m2K. 

 

Yum Yum Yum! 

 

The right side actually looks very similar to my design, except I was having the insulation outboard of the OSB- however further reading, you can run into moisture retention and/our internal vapour and temps causing condensate to gather outside the vapour barrier but stuck in the outboard insulation which can lead to mould which is obviously not great. My order of sealing details are water, air, vapour, thermal... so if I can get the first 3 done- the last should be self supporting when the insulation is in, but running the vapour-open insulation before the main insulation with the service cavity is a nice touch, I'm going to revisit some of my modelling in the next coming weeks once the design of the house itself is done and signed off by an architect, then rest of the actual structural stuff comes after.

 

On another note, I just spent a small fortune on reading materials. I picked up the IBC 2021, Building Regs 2010 (2021 edition, with Part L for energy conservation), Scottish small dwellings guide, eurocode 5 and BSI BS-8103 all stacked up for reading materials for my next few weeks 🙃

[AccidentalSkydiver]

On 18/03/2022 at 18:49, TerryE said:

Our Larson strut cassettes were assembled in factory on assembly jigs.  Too much of a PITA making these up on site, IMO

Ehh maybe, but if you setup a backstop and a decent jig you could easily build out the idea of a non-structural double stud setup - you just need to keep two studs parallel and equidistant and then have some slots for your spaced blocking to go- if you went with 2ft OC (600mm) from a 2400mm stud you're looking at 4 blocks, if you went side on and not down the middle, you'd 'simply' need to have them ripped down the your given size- in my image below I'd assume 180mm width, 100mm height 
 

On 18/03/2022 at 19:11, Simplysimon said:

so why not go a 245-300mm i beam wall and build onsite?

 

Because I'm an awkward git? 😁 I'm 100% going to be framing traditionally, but I may add an additional non-structural semi-larsen style outer layer before the masonry - however if I did this, I was preferably looking to run our double stud layer externally of the shear walls off set from the studs in the shear wall to stop the thermal bridging and moving the offset of any air gaps. Here's a quick example I've got in my head ...35mm stone slip, 100mm thermal blocks, 45mm gap, 18mm osb3, 180mm gaps for insulation, with side-blocked 37x37mm battons which are spaced 500mm OC, then the 18mm OSB, 2x6 600mm OC on a 2x6 sill. I'd have the 'lower' one perpendicular to the axis I'm following, starting at the point of the lowest external block (If that makes sense... I've only had one coffee today and 7 meetings)

With the offset there would be some places where thermal bridging can occur (the corner here for example) but with offset timbers and air gaps you'd be able to bring that down to a minimum. Then add in something like the proclima kaflex for sealing protrusions for cables, or roflex for pipes - I'd be pretty confident that it will create a very warm and comfortable home.



 

[TerryE]

@AccidentalSkydiver out of interest if you google youtube MBC timber, then you'll get lots of examples.  Here is one example which shows their warmslab and Larson struct cassette builds. 

 

In terms of your profile a few thoughts:

• You only need one racking layer and also a vapour barrier on the inner surface of the TF.  You can use something like 12 mm OSB3 for this.  If your verticals are at 40mm centres then you can join the OBS on every 3rd upright (or 2nd if you use 60mm centres).  (These would need tweaked so save a lot of OSB ripping, if you are buying in 1220 OSB rather than 1200s.)  We then had 44×25 battens oner-pinned on the vertical upright lines after taping up the OSB butt joints, to create a service cavity.  This made first-fit a doddle.  (Your SE would need to sign-off on 40 vs 60, racking, etc.)
• I can't see any advantage in having an outer OSB layer between the main TF verticals and the standoff fill section.
• In terms of the stand-off, remember that you need to tie this structurally to the outer blockwork leaf.  The ties need to anchor to something in the TF.  This will require some decent uprights that are tied to the main TF uprights, say 38 x 63 CLS minimum and made up a frame to mirror the main TF.  You would need some structural spacer noggins to stand the outer TF from the inner say 60 × 89 × 38 if you want a 300mm fill void, but you could easily up the 60 to fit whatever you paln as the profile.  You'd want some form of through anchor to fix the two frame; probably the simplest method would be to use 200mm timber fixing to drive through the out CLS, the standoff and into the inner TF.
• The vapour breather (panelvent + membrane) layer goes on the outside of the outer TF.  Mark the upright lines so you know where to fix the ties.  Remember that you want the frame to breath outwards, not inwards. 
• Put in through-pipes for any services that you need to take through the frame.  These pipe exteriors can be sealed to the frame for air tightness and the the pipes themselves foamed and sealed once the services has been pulled.
• You can leave the cellulose blowing until before 1st fit.  (Our guys just cut a 100mm hole at the top of each panel section and pumped the stuff in section by section, then taped up the hole.)      

Edited March 21, 2022 by TerryE

[Russell griffiths]

You want to forget any type of lightweight thermal block if you are using stone slips, the adhesive will not like the thermal blocks, you will end up using so much primer and additives, much better of with an aggregate block. 

[SteamyTea]

3 hours ago, AccidentalSkydiver said:

On another note, I just spent a small fortune on reading materials. I picked up the IBC 2021, Building Regs 2010 (2021 edition, with Part L for energy conservation), Scottish small dwellings guide, eurocode 5 and BSI BS-8103 all stacked up for reading materials for my next few weeks 

Are they .pdfs.

If so, are you willing to share?

[AccidentalSkydiver]

38 minutes ago, SteamyTea said:

Are they .pdfs.

If so, are you willing to share?

Yep couple are, but the IBC and BS 8103-3 are physical copies, got the BS one through work (after some bribing persuading the team in purchasing with coffee and cake to let me buy it through the department and I'd pay back at the member price rather than full cost). IBC I bought online shipped to my door

Some of the links:
Eurocode EN1995-1: https://www.phd.eng.br/wp-content/uploads/2015/12/en.1995.1.1.2004.pdf
Building Regs 2021 with Part L: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1057372/ADL1.pdf
Scottish small buildings guide: https://www.gov.scot/binaries/content/documents/govscot/publications/advice-and-guidance/2020/02/the-small-buildings-structural-guidance/documents/small-buildings-structural-guidance/small-buildings-structural-guidance/govscot%3Adocument/Small%2BBuildings%2BStructural%2BGuidance%2B%2B.pdf

Alot of these I was specifically looking for span calculations for flooring joists and fire bridging standards- IBC was particularly one I was super interested in since the majority of North American homes are TF, California has a specific sub section in their own local codes for fire bridging, and then Alaska / Canada etc have good local codes for Cold and thermal insulation details I've been paying attention to on my travels....

[AccidentalSkydiver]

2 hours ago, TerryE said:

@AccidentalSkydiver out of interest if you google youtube MBC timber, then you'll get lots of examples.  Here is one example which shows their warmslab and Larson struct cassette builds. 

 

In terms of your profile a few thoughts:

• You only need one racking layer and also a vapour barrier on the inner surface of the TF.  You can use something like 12 mm OSB3 for this.  If your verticals are at 40mm centres then you can join the OBS on every 3rd upright (or 2nd if you use 60mm centres).  (These would need tweaked so save a lot of OSB ripping, if you are buying in 1220 OSB rather than 1200s.)  We then had 44×25 battens oner-pinned on the vertical upright lines after taping up the OSB butt joints, to create a service cavity.  This made first-fit a doddle.  (Your SE would need to sign-off on 40 vs 60, racking, etc.)
• I can't see any advantage in having an outer OSB layer between the main TF verticals and the standoff fill section.
• In terms of the stand-off, remember that you need to tie this structurally to the outer blockwork leaf.  The ties need to anchor to something in the TF.  This will require some decent uprights that are tied to the main TF uprights, say 38 x 63 CLS minimum and made up a frame to mirror the main TF.  You would need some structural spacer noggins to stand the outer TF from the inner say 60 × 89 × 38 if you want a 300mm fill void, but you could easily up the 60 to fit whatever you paln as the profile.  You'd want some form of through anchor to fix the two frame; probably the simplest method would be to use 200mm timber fixing to drive through the out CLS, the standoff and into the inner TF.
• The vapour breather (panelvent + membrane) layer goes on the outside of the outer TF.  Mark the upright lines so you know where to fix the ties.  Remember that you want the frame to breath outwards, not inwards. 
• Put in through-pipes for any services that you need to take through the frame.  These pipe exteriors can be sealed to the frame for air tightness and the the pipes themselves foamed and sealed once the services has been pulled.
• You can leave the cellulose blowing until before 1st fit.  (Our guys just cut a 100mm hole at the top of each panel section and pumped the stuff in section by section, then taped up the hole.)      

Assume you mean 400mm/600mm? 40mm would be a fairly small space 

Outer layer OSB was to add an additional air break, but offset moving any direct line of air gap off set in an event that air sealing was not properly done or broken. however, this could be easily replaced with meshing or depending on the material of outer insulation simply a good tape like gapotape to create the fit

You are correct about the blockwork leaf needing to be tied in, this was a oversight on my part - boredom in a meeting I really didn't need to be at, but was forced to be in + lack of coffee = this, but I did spend some time after my original drawing here looking at a few different larsen/double stud walls, and found most sat the secondary layer in-board, using the shear outside with blocking or osb to secure the inner wall with the insulated gaps between with vapour barriers in place. regarding the marks for the vapour barrier etc - agreed, definitely through marking would help finding studs, its a common enough practice  

  

1 hour ago, Russell griffiths said:

You want to forget any type of lightweight thermal block if you are using stone slips, the adhesive will not like the thermal blocks, you will end up using so much primer and additives, much better of with an aggregate block. 

Ah Nice, I'll look into this - Some of the companies I'd looked at (and spoke to) mentioned it would work but I never really asked about how much work it would need to make it work... if that makes any sense at all 😁

[Iceverge]

6 hours ago, AccidentalSkydiver said:

 I'm going to revisit some of my modelling in the next coming weeks once the design of the house itself is done and signed off by an architect

 

Make sure you have enough wall thickness in the plans, with a block exterior + stone I would be looking for an absolute minimum of 500mm. You could use a cement board over a cavity only as backing for the stone instead of block, It wouldn't be cheaper and may cost more in house insurance however.  Do PHPP before the signoff too. 

 

5 hours ago, AccidentalSkydiver said:

Here's a quick example I've got in my head ...35mm stone slip, 100mm thermal blocks, 45mm gap, 18mm osb3, 180mm gaps for insulation, with side-blocked 37x37mm battens which are spaced 500mm OC, then the 18mm OSB, 2x6 600mm OC on a 2x6 sill.

 

The 37mm*37mm battens would be very bendy to try to work with. Typically people say unless it's at least 89*38 don't bother. OSB is not cheap.  You have 2 layers.  Also a lot of labour. As you plan on doing lots of the building yourself plan your time economically. It takes 3 times longer than you normally estimate in my experience.  Lots of the North American construction is a little bit one dimensional. Happily installing a single paned vinyl window with terrible air sealing in an r30 wall makes no sense or putting an 18 inch twinwall on a slab with 2 inch polyiso screams of designers who haven't bothered to so the calcs.  

 

If you were set on the twin wall a double stud rather than Larsen truss could be easier to build on site as well as significantly cheaper. 

 

Here is an example. https://passivehouseplus.ie/articles/renewable-energy/on-the-plus-side

 

With this you all but eliminate your wall-floor thermal bridge and the wall-ceiling. Your band joist area remains but this isn't as big as you think. You can drop to 1 layer of OSB externally for cost. I would still include an internal vapour barrier and service cavity. If you start playing with PHPP or even Jeremy's calculator here you'll see how much more important airtightness is than outright U values. Also thermal bridging is extremely important.  It can take a bit of setting up but the free software THERM is a great free tool if you have the patience. 

 

 

On this also, an external layer of woodfiber will provide really terrific over insulation of window frames and is almost fool proof to get right unlike detailing internal thermal breaks in timber walls.   

 

 

Have you played with https://www.ubakus.com/en/r-value-calculator/. Again looking at your sketchup drawings I think you'd enjoy it! 

 

 

 

 

 

 

[Simplysimon]

6 hours ago, AccidentalSkydiver said:

Because I'm an awkward git? 😁 I'm 100% going to be framing traditionally,

ok, a few of us here are as well, a 350mm I beam kit wall, 600mm c/c studs, mdf outer skin (breathable), osb internal with service cavity and blown cellulose is the way i've built as well as @Patrick and possibly a few others with variations and can be stick built on site. would seem to be a lot easier than your method. keep it simple

[AccidentalSkydiver]

58 minutes ago, Iceverge said:

 

Make sure you have enough wall thickness in the plans, with a block exterior + stone I would be looking for an absolute minimum of 500mm. You could use a cement board over a cavity only as backing for the stone instead of block, It wouldn't be cheaper and may cost more in house insurance however.  Do PHPP before the signoff too. 

 

 

The 37mm*37mm battens would be very bendy to try to work with. Typically people say unless it's at least 89*38 don't bother. OSB is not cheap.  You have 2 layers.  Also a lot of labour. As you plan on doing lots of the building yourself plan your time economically. It takes 3 times longer than you normally estimate in my experience.  Lots of the North American construction is a little bit one dimensional. Happily installing a single paned vinyl window with terrible air sealing in an r30 wall makes no sense or putting an 18 inch twinwall on a slab with 2 inch polyiso screams of designers who haven't bothered to so the calcs.  

 

If you were set on the twin wall a double stud rather than Larsen truss could be easier to build on site as well as significantly cheaper. 

 

Here is an example. https://passivehouseplus.ie/articles/renewable-energy/on-the-plus-side

 

With this you all but eliminate your wall-floor thermal bridge and the wall-ceiling. Your band joist area remains but this isn't as big as you think. You can drop to 1 layer of OSB externally for cost. I would still include an internal vapour barrier and service cavity. If you start playing with PHPP or even Jeremy's calculator here you'll see how much more important airtightness is than outright U values. Also thermal bridging is extremely important.  It can take a bit of setting up but the free software THERM is a great free tool if you have the patience. 

 

 

On this also, an external layer of woodfiber will provide really terrific over insulation of window frames and is almost fool proof to get right unlike detailing internal thermal breaks in timber walls.   

 

 

Have you played with https://www.ubakus.com/en/r-value-calculator/. Again looking at your sketchup drawings I think you'd enjoy it! 

 

 

 

 

 

 

I'd picked 37x37mm off top of my head without consulting my tape measure... things are always a bit bigger in your minds eye aren't they 🤣 but with the two layers, I'd expect plenty of shear strength with the cross sectional rigidity being created with the sheathing and then the actual main structure (since this would essentially be a stand off and run flat and perpendicular to the supporting wall.  You're probably correct though, they'd be a bit bendy - I suppose with a 3 / 3 layout at 400mm OC you'd have more strength if you put them on alternating sides... Quickly added a 400mm OC model into a setup in fusion, going to strength model this tomorrow when I have some more time!

Yeah I've noticed the flange fit windows and then the super-raving about 'European style UPVC tilt turn' conventional windows here- it is a bit boggling you'd spend the time and money insulating to stick on flange fit which are so poorly sealed in the rough opening... 

Did utility in 39x89 which is solid, but it was also a fairly small area and a single wall to enclose the flat roof+ an inside walls in the old coal house/pantry. I just did sill seal and a basic rock wool in that area though

I understand wood and OSB especially are not cheap - just the few projects I've done in the past year for people have been a bit mad for the materials compared to even 18 months before, however, I've already got a costing sheet I'm using to add up the current expected cost of framing including joists, trusses, rim joists etc with an average of 10% over purchase and a contingency of another 3k - but that might change.

Alot of my current plans I've sketched up (confusingly I've done a fair bit of it in Fusion) have an additional 18mm inboard for plasterboard + the external sheathing where needed, plus a 36mm layer in the garage dividing wall for fire insulation - however, I realised I can likely use a single fire-rated plasterboard - Cheers for the resources, I'm going to play with ubakus now

Edited March 21, 2022 by AccidentalSkydiver

[TerryE]

13 hours ago, AccidentalSkydiver said:

Outer layer OSB was to add an additional air break ...

To quote Elon Musk: the best part is no part.  You only need 1 air barrier.  You need to seal this by construction design.  Eg. Sika tape the OSB joints and then top with the service cavity battens.  The filler needs to breath outwards from the barrier through the Panelvet and outer breather membrane.  As others have said extra cost and work for negative benefit.

 

Lastly having added quite a few service through pipes on my twinwall after the cellulose had been blown / filled, it is amazingly dense so with the inner OSB is pretty airtight. I used a 60cm 15mm bit to pilot inside to out; then a 25 / 40mm / whatever hole cutter on the inside and out; then notched the end of the ABS 25mm / whatever with a sawtooth so I could twist / cut its way through to maybe 5mm excess on one side and multitool off excess on other. Silicon and Sik tape to finish.