What are PSI values?

PSI values play a pivotal role in understanding heat loss in buildings, particularly at intersections where different building materials and geometrics converge. So, what are PSI values? Essentially, these values quantify the heat loss when the building fabric changes direction or it geometric structure.

 

What is a PSI value calculation?

A PSI calculation involves measuring the total heat loss in a building. These calculations take place during the design of new-build construction projects and are crucial in determining where amendments need to be made to reduce heat loss and improve energy performance.

The measurements are taken through the junctions of the building. These junctions include meeting points like the point between the ground and an external wall. PSI values help identify where buildings can be made more energy efficient by indicating areas where there is a loss of energy between two thermal elements. Essentially, it measures the linear thermal transmittance in building.

 

Why are PSI values calculated?

A PSI value calculation plays an important role in energy performance and meeting building regulations.

To minimise heat loss from the interior, a buildings insulation (known as the thermal envelope) should be continuous. Continuous insulation is most at risk at junctions between two thermal elements, such as where the walls and floor meet. This is usually because structural considerations take precedence.

For example, a cavity wall construction where the inner leaf of masonry must continue down to the foundations to transfer to loads it bares into the ground. The ground floor insulation stops at the face of the masonry and cannot be continuous with the insulation layer in the cavity wall.

By interrupting the continuity of the thermal layers, the masonry acts as a thermal bridge. The heat loss through that thermal element is greater than the relatively well-insulated construction on either side of it.

There are ways to reduce ther thermal bridging effect, but it must still be accounted for as part of establishing the whole building’s thermal performance.

 

Psi Values are provided in accordance with R497 and EN10211 to calculate the linear thermal transmittance. 

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Suitable Junction Types:

E1 Steel lintel with perforated steel plate

E2 Other lintels (including steel lintels)

E£ Sill

E4 Jamb

E20 Exposed floor (normal)

E21Exposed floor (inverted)

E6 Intermediate floor within a dwelling

E7 Party floor between dwellings (in block of flats)

E8 Balcony within a dwelling, wall insulation continuous

E9 Balcony between dwellings, wall insulation continuous

E23 Balcony within or between dwellings, balcony support penetrates wall insulation

E10 Eaves (insulation at ceiling level)

E24 Eaves (insulation at ceiling level - inverted)

E11 Eaves (insulation at rafter level)

E12 Gable (insulation at ceiling level)

E13 Gable (insulation at rafter level)

E14 Flat roof

E15 Flat roof with paparet

E16 Corner (normal)

E17 Corner (inverted- internal area greater than external area)

E18 Party wall between dwellings

E25 Staggered party wall between dwellings

P1 Party wall - ground floor 

P6 Party wall - ground floor inverted

P2 Party wall - intermediate floor within a dwelling

P3 Party wall - Intermediate floor between floors (in blocks of flats)

P4 Party wall - Roof (insulation at ceiling level)

P5 Party wall - Roof(insulation at rafter level)

R1 Head of roof window

R2 Sill of roof window

R3 Jamb of roof window

R4 Ridge (vaulted Ceiling)

R5 Ridge (inverted)

R6 Flat ceiling

R7 Flat ceiling (inverted)

R8 Roof to wall (rafter)

R9 Roof to wall (flat ceiling)

R10 All other roof or room in roof junctions

R11 Upstands or kerbs of rooflights

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Benefits of using thermal modelling in construction.

 

1 Meet building regulations

All construction sites must follow several regulations to continue building and complete the project successfully.

Building regulation calculations with thermal modelling will ensure that you comply with Part L of the Building regulations.

 

2 Environmental Efficiency

The UK government has set ha set a timetable for new low energy efficiency standards to lower carbon emissions without retrofitting, offering construction companies time to prepare for a 70 to 80% reduction in carbon emissions.

With the correct building regulations and SAP calculations in place, your construction project will reduce its carbon footprint and comply with new standards.

 

3 Save time

Calculating PSI for home and commercial sites with us can help you save a lot of time. This can help your projects SAP rating and reduce the need for other energy efficient measures in your development to pass SAP assessments.

 

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Why Choose Us. 

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Choosing Yourspace means you get friendly, fully trained, certified and accredited assessors who work with BRE approved software packages such as JPA Designer, and AUTOPSI. We keep you fully informed until the assessment is successful and our reports contain building Control required information ensuring a speedy progression of your development.