Concrete Floors

So here we are again, with some more super action shots of concrete! The decision was made to use a pre-cast concrete floor in these houses for a variety of reasons including,
The extremely good sound resistance of concrete floors both impact and airborne and allows the use of concrete partition walls at first floor.

The external walls and internal partition walls where taken up to chamber level and the floor is craned into place,

The concrete planks have been designed and produced specifically for this site and are laid onto the 190mm thick external wall ensuring that there will be enough room to construct a 100mm block wall which will act as a shutter for the concrete.

Once the 100mm course of thin joint blockwork has been installed a wooden shutter is constructed around the stairwelland as seen here the floors are kept separate at the party wall junction. As there is no Robust Detail for a solid party wall used with a solid concrete floor each dwelling will require pre-completion testing.

Additional steel has been designed for this floor and installed as shown. One important aspect of a Passive House is the ventilation system, this project has a Mechanical Ventilation with Heat recovery system and the ducting will be hidden within the concrete floor. 

Concrete is pumped into place and is power floated to produce a smooth hard wearing finish which is ready to accept the required floor covering.

External Walls

Here we are after a slight delay, back on site. The external walls are now up to chamber, pictures here show the 190mm external walls being constructed from a new aircrete block with a thermal conductivity of 0.07W/mK and have a bed tolerance of just ±1mm which allows, as you can see, Clan Thinset mortar to be used to create a mortar joint of just 2mm.

When using Clan Thinset mortar the blocks are bonded together to produce a homogeneous aircrete wall, you can see a red mesh on one of the joints. This is Clanmesh which is a glass fibre fabric which has been specially designed and tested for use in Thinjoint mortar. Clanmesh distributes any stresses which may build up in the wall.

 

This method of construction produces a virtually airtight wall which will not require a membrane to achieve the 0.6 SCH air (changes per hour) required by the Passiv Haus Institute.

The party wall on this pair of semis is being constructed from a dense concrete block wall laid with Thinjoint mortar. This is not normally possible because the tolerance on the bed faces is not good enough to achieve the 2mm joint. However, when the blocks are laid on their side the bed face becomes the parallel side formed from the mould side when the blocks are manufactured. This method of build overcomes the problem of creating an airtight party wall, a thermally efficient party wall and achieving a sound test of of 60Db.

First Course of Blockwork

The first course of blockwork is laid onto the reinforced concrete slab. A DPC is placed adjacent to the perimeter insulation which is formed by the upstand of the sub-foundation insulation.

 This first course is laid on a bed of sand and cement mortar to level out any imperfections in the raft. The vertical joints are bonded with Thinset mortar to ensure the bond is kept in subsequent courses and also adds a little rigidity to the blockwork.






The blocks are manufactured from a material which would normally go to landfill, this is added to a little cement to act as a binder and aluminium which expands in the mix to produce a concrete block with millions of air bubbles. This process is not unique but we have found a way of producing the block to give the best thermal value of any aircrete block on the market with a thermal conductivity of 0.07W/mK almost 35% better than the standard 0.11W/mK.

The 190 wide blocks are laid with Thinset mortar whichbonds the blocks together with a 2mm joint. This is possible because the blocks are manufactured to a tolerance of ±1mm. The mortar is applied with a notched trowel which delivers a pre-determined amount of mortar to the block. This allows a fast but more importantly precise method of building, minimising thermal bridging and ensuring airtightness as the wall is built. 

Steel and slab

Still with the boring stuff, unless you're an engineer! Here we have photographs of the steel, one interesting point here is we couldn't change the thickness of the raft so where the party is located you can see that  we have added additional steel.

Concrete is pumped in to produce a fairly shallow raft of 200mm thick. Note the ground was backfilled up against the block to provide support to the insulation, this also provides protection against frost heave. Having a shallow foundation increases the possibility that the ground could freeze below the sub foundation insulation, in severe weather conditions. The concrete wall will provide protection against frost heave as well as acting as a permanent shutter for the raft.

Foundations

This pair of Passive Houses will have a sub foundation insulation; A standard method used in Germany but one of the first times it has been used in the UK.

The topsoil is scrapped away and a shallow trench is dug for a small retaining wall.

Before the sub foundation insulation is placed a dwarf retaining wall is built

This is not load bearing but is purely to support the insulation 

600mm of Extruded polystyrene with a density of 45Kg/M3 and a thermal conductivity of 0.032W/(m.K) is placed around the perimeter of the wall.

The hardcore is then sand blinded to produce a flat level base ready to receive the insulation.

Slabs of insulation are then placed carefully over the expanse of the foundation

 

The foundation insulation is then increased in thickness laid over previous layers crossing the junctions of the preceding layer to improve the load bearing capacity. A total thickness of 300mm is finally placed

Finally an impervious membrane is laid over the polystyrene which acts as a gas barrier and protects the insulation from damage when the concrete is poured

Who What When Why

Low Carbon Construction is attempting to build a pair of semi-detached houses for the social / affordable housing sector constructed from solid wall masonry and will be certified as a Passive House.

The site owner is Blythe House Lettings Ltd and this project is part of an overall scheme of 8 units which are all being built by the main contractor - Low Carbon Construction Ltd. Clan Products NW will supply the the materials to enable Low Carbon Construction the build a Passive House shell through their company Thin Joint Technology. Toby Rollason from Lune Architects have adapted a previously consented planning permission for the pair of semi's to ensure they meet PassivHaus standard and are working with the Scottish Passive House Centre (SPHC), who will monitor the project and ultimately provide accreditation.

A Passive House must achieve a number of defined targets, 

1) the heating demand must be less than 15 KWH/M2 per year and that the total energy demand for heating, hot water and domestic appliances should be no more than 42 KWH/M2.

2) The air changes must b less than 1m3/(h.m2)@50Pa

3) The windows (frame and glazing) should be less than 0.8W/m2K - triple glazed

The owners and workforce of Low Carbon Construction Ltd have many years experience using modern methods of construction and producing very high quality builds to exacting standards. This will be their first certified PassivHaus build and with a tight budget based on standard build costs, the objective is to prove that PassivHaus can be a cost effective solution to provide low cost and affordable housing. In this difficult economic climate Low Carbon Construction Ltd believe they can replicate the quality assurance of certified PassivHaus units across the social housing sector at a cost comparable to traditional build. With energy costs set to rise astronomically over the coming years Low Carbon Construction Ltd believe they can be instrumental in addressing fuel poverty.

First Days

Welcome to the Blogspot for the No Mans Heath Passive House

This blog has been posted to keep up to date with the build of a pair of semi detached houses which will be built to the Passiv Haus principles and certified by the Passiv Haus Inst Germany.
This will be the first semi-detached to be built for a RSL and certified by the Passiv Haus Institute.
We intend to provide you with a weekly update of how the build progresses and what problems have to be overcome during the course of the build.
Fortunately Low Carbon Construction are well versed in using modern building materials but this build will introduce some new products to create a Super Insulated Masonry house.

Chris Hirst Director of Thin Joint Technology Ltd