Efficiency V Budget (new Build

Shanaknocker

hi All.

I am a newbie, on Boards and a self build project. I figured that the best place to get advice is on here, however I believe that in order to get advice one must give it too. I wanted to start this tread in order to get information about aspects relating to heating, renewable's and energy.
I am intending on building a 210 m sq house in West Cork. We have received planning for a split level house, which does not have a huge gradient. I am 90% sure that i will be using a block on the flat (220 mm) with 200mm of external insulation, witch should achieve a u-value of 0.15 (if not an insulated slab inside will). it will be built on a slab (passive standards) with a roof structure that i hope will be of similar U-values. I am putting in tripled glassed windows and hoping to achieve a air tightness of .6 air changes per hour.
My open plan single story section is south facing with 4.5 m of glassing facing south and 1.5 facing east and west. I'm a little concerned with over heating, i have a over hang for half of the south facing that will stop summer sun, but the rest may cause over heating.
I am building this to tight budget of 210. yes I am aiming to build to the best standards for the cheapest route possible, without affecting quality, especially on the fabric of the house.

I hope my journey will educate others in self building and also steer me along the way

sydthebeat

to protect against over heating, elements of passive (as in not mechanical) design should be considered such as ability to cross ventilate a room, wider overhangs etc.
if you want to scientifically assess whether over heating will be an issue then really the only way to do that is to get a full passivhaus assessment carried out.

a few comments so far:
1. insulated boards on the internal when you have external insulation is madness. If you require a lower wall u value, just increase the EWI

2. if your on a strict budget and your looking at wall u value levels of 0.15 but also looking at insulated foundations, then i think you might eventually start to look at standard cavity wall with full fill 150 PIR (0.14 u value) as being a more realistic option

Shanaknocker

syd...... I agree that putting insulated slabs is counterproductive and will reduce the thermal mass and may cause mold, so we will scratch that idea. I have a BER and DEAP reports been conducted so will know more soon.
I put the idea of cavity out of my head when I first started researching, (maybe tried too hard to get away from the traditional build) and i researched timber frame, ICF, SIP panels (even going as far as researching magnesium SIP panels from Poland and finally stuck on flat block and external insulation.
Builder told me that either way would be around the same cost, but i now know that plastering onto external insulation is a lot more expensive.
Can i ask what PIR is? might look at traditional again.!!!

Have you built?

Calahonda52

Polyisocyanurate (PIR) insulation board.

I very much doubt if you will do 210 for 210 with that spec in split level.

Whats the plan for the A/T layer to achieve 0.6

have you thought through the overhang from both a shading perspective and thermal bridging with EWI

Whats the heating/ventilation plan?

Whats the plan for fixing the windows with the EWI: what the build sequence.

Are all services in the 210: elec, water sewage etc

ps, I have not built:D

Shanaknocker

hey Calahonda52,
thanks for PIR information, I have been told that i will struggle to keep it at 210, I am going to be doing a lot of the internal finishes myself, plumbing, laying floors, tiling, doors, painting and hopefully pulling wires and ducting for MHRV, so this will reduce a chunk of the cost. Yes it may be longer but cheaper.
A/T i am going plastering inside with sand and cement (have been told that this will give me A/T) membrane on the ceiling that will be taped to the walls. Tape around the windows(inside and out) ??????? not sure if I can do any more, I thought about putting plastic around the blocks before external insulation but not sure f i need it.
over hang is only over sliding door area, my jutting out dining area may be an issue but i can attache some shading after wards or external blinds. will know more after first year.
Windows windows windows. I have detail where the windows are 3/4 on the block (taped inside). A notch will be taking out of the external insulation to encase the window outside. this may do, otherwise i was looking at putting similar insulation that is in the foundation around the window frame before the window goes in. (suggestions would be welcomed)

Don't get me started on the heating. Probably looking at 6-8Kw pump for DHW and low tem rads (not sure on UF yet as i don't think i will need it) ( waiting on BER guy to get back to me on heating demand). I was looking at a post heater (water grill) attached to MHRV to maintain the air tem at 21 degrees but i do believe this is a slow process and this may not heat the house if it gets to cold. I will have a stove and a ducting going from stove to the hall way, as to transfer some heat away from living room to other areas.

What do you think of thermodynamic panels? I have been told that they are good for DHW 365 days a year, if this is so can they be used alternatively every hour to heat the water grill?????, thus keeping the air temperature up. thus i could put in a stove with a back boiler to heat rads.

Calahonda52

OP, the above post has so many issues in it that I don't know where to start so all I can suggest is that you read
https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx
while it is aimed at renovation the science is the same for new build.

There is also plenty information on other threads here.

It is time for you to invest in some professional advice as you risk making the house perhaps unliveable in.
I am all done here.

Shanaknocker

Thanks Calahonda52 for your input.

I will hopefully be posting here regularly as the build gets up and running and wish to get as many individuals involved as a way of documenting the build. Hopefully dig out will commence mid June.

Ps how do you add photos
and how do people use the quote things i see on other treads. when i press the "quote button, all the post appears, i take it that i chop what i don't need. but what does the +" button do.

BarneyMc

Shanaknocker wrote: »

Thanks Calahonda52 for your input.

I will hopefully be posting here regularly as the build gets up and running and wish to get as many individuals involved as a way of documenting the build. Hopefully dig out will commence mid June.

It's early May and you hope to dig out mid June and you've all the above questions? From my experience as a self builder you really should have every major detail in place before you start your build. It's not nice/possible having to make major decisions during a build.

Shanaknocker

To all that follow.

We have decided on block on the flat (215 mm). A TC (thermal Conductivity) of 1.33
200 mm of external insulation. A TC of .031
15 mm of sand and cement (internal) .015
10 mm Gypsum plaster .0232
total resistance is 6.65145
U- value calculations are 1/ 6.65145= 0.15034
Still waiting for the Thermal conductivity of the external plaster, but not expecting u-value to drop much. Happy with this.

My roof will be sitting on a thermo block, which will reduce the cold bridging.

There is a sloped section and flat section to my ceilings both in the single story (due to high ceilings) and second story as we had to keep apex of roof to a certain height.
I will be using 7 in joists (177 mm) with 150 mm of PIR insulation in between the joists. I will put 50 mm insulated slab on the internal aspect of the ceiling. Any other suggestions would be appreciated here.

Tripled glazed windows, which will overhang the concrete wall (outside) and the external insulation will encase the rest of the frame. Passive sills will be at the base of the windows, no cold bridging.

My BER has come back stating that there will be a heat requirement 4932 kwhr/yr, if i divide this by 210 sqm this will give me a figure of 23.49 Kwhr/m2/yr.........????? yes or no
it is also saying that i will have a heat loss of 238WK per msq.

Trying to understand this,





calculations for U-Value are coming in at

chillit

Shanaknocker wrote: »

To all that follow.

My roof will be sitting on a thermo block, which will reduce the cold bridging.

the thermal block is a good idea but also you should make sure that your roof insulation meets the wall insulation. This will be the best approach to removing any thermal bridges at the wall/roof junction

chillit

you say

"I will put 50 mm insulated slab on the internal aspect of the ceiling. Any other suggestions would be appreciated here. "

Where are you putting the vapour and airtightness barrier ? Are you leaving a counter battened cavity for services. This is usually recommended to avoid penetrating the airtightness layer

Shanaknocker

chillit wrote: »

Where are you putting the vapour and airtightness barrier ? Are you leaving a counter battened cavity for services. This is usually recommended to avoid penetrating the airtightness layer

I initially had the 50 mm insulated slab only on the sloped section and was going to put rockwool or earthwool on top of the joists, however i was told that this may cause my joists to sweat and cause condensation???. my airtight barrier will be on stapled to the joists before slabs go up and extreme caution after. I presumed the vapour barrier will be on the outer side of the rafter???