# HVAC

Image: Stuart Miles / FreeDigitalPhotos.net

#### Calculating Water Efficiency

With the impending changes to part G of the building regulations this online tool will be invaluable The Water Efficiency Calculator for New Dwellings

#### Calculating Calorific Value

Read this article on calculating the calorific value of natural gas

#### Glass Solar Heat Gain Coefficient - SHGC

Glazing solar heat gain coefficient explainedGood article which describes the difference between the solar heat gain coefficient and shading coefficient. Useful to understand for calculating solar heat gains.

#### Installing water pipe in contaminated ground

Cold water service pipe installed in contaminated ground should either be Table Y blue polyethylene coated copper pipe or MDPE barrier pipe e.g. Protecta-line by GPS PE Pipe Systems or Trigon by Wavin or Puriton barrier pipe by RadiusIn addition all joints must be wrapped with serviwrap, denso or equivalent tape; as few buried joints as possible should be used and the trench should be in-filled with clean imported bed surround and fill materials. The installation would need to be approved by the water authority whom may impose other restrictions.

#### Thermal Conductivity

Thermal conductivity (lambda value - W/mK) is the capacity of a material to conduct heat, or in the case of an insulating material the capacity to resist heat transfer. It is considered that materials are thermal insulants if their conductivity is less than 0.065 W/mK.**The lower the thermal conductivity value of a product the better it is as an insulant.**The thermal conductivity of a typical mineral fibre product is in the range of 0.034 to 0.044 W/mK, whereas a good rigid phenolic insulation thermal conductivity is in the range of 0.021 to 0.024 W/mK. Therefore phenolic is better than mineral fibre. Find out more about phenolic insulation

#### Thermal resistance

Thermal resistance (R value - m^{2}K/W) is the capacity of a product to resist against heat loss.

**A product with a higher R value will perform better as an insulator.**The thermal resistance of a specific product can be found by dividing its thickness by the thermal conductivity.

#### Part L 2010

A very informative blog on Part L2A 2010 can be found here Part L2A 2010 – worked case studyThese links open in a new window

**Corn**is a free resource by homemicro.co.uk, full details here...