Chapter 7 Energy Building PerformancePP

Question 1

In Fig. 1 the glazed roof of the conservatory has a rate of heat loss of 604.8W when the temperature inside is 18°C and the temperature
outside is −2°C. Calculate the U value of the glazed roof. area= 10.8
Show your working out in the space below

Answer 1

U value = 604.8W/
10.8m2 × 20°C
u = 2.8 Wm–2K–1

Question 2

Calculate the new rate of heat loss through the conservatory roof if the temperature outside increases to 8°C. You should assume that all other variables remain constant. Show your working out in the space below

Answer 2

rate of heat loss = area x u value x temp diff

10.8m2 x 2.8 x 10 = 302.4W

Question 3

The Code for Sustainable Homes (CSH) is an environmental assessment method for rating and certifying the performance of new homes. It measures the assessment score across nine categories of
environmental impact. Identify two of these categories.

Answer 3

water, waste

Question 4

Discuss how the energy efficiency of a building could be
influenced by the following factors:
Insulation
Air tightness

Answer 4

Insulation to roofs/lofts will reduce heat loss and improve energy efficiency

Insulation can be added to floors and to solid/ cavity walls to reduce heat loss and improve energy efficiency

Insulating hot water tanks, hot water pipes and behind radiators will reduce heat loss and improve energy efficiency

Poor air-tightness in the building envelope leads to draughts which let in cold air and waste too much heat

improve air-tightness by blocking up unwanted gaps (e.g. by installing draught excluders on doors/ windows; blocking up old chimneys)

Better air-tightness will reduce heat loss & improve energy efficiency

Question 5

a household install insulation in the roof loft, outline one environmental advantage of this

Answer 5

reduced carbon emissions

Question 6

describe 2 measures to improve the energy efficiency of the outside of rooms

Answer 6

improving air tightness of windows, reducing heat loss through the window,
improving glazing (double/triple) will reduce the heat loss through the windows as improved u-values

Question 7

describe what is meant by the u-value of a material

Answer 7

the u-value for a material is the rate at which heat is conducted away through 1m2 of the material for each 1 degree difference in temperature between the external and internal of the building

Question 8

zero carbon homes hierarchy

Answer 8

top - allowable solutions
bottom- fabric energy efficiency

Question 9

explain 2 requirements for a zero carbon home

Answer 9

the fabric performance must comply with the FEES
any co2 emissions remaining after heating, lighting etc must be less than or equal to the carbon compliance limit

Question 10

Outline two different ways in which they might changes their day to day behaviour in order to minimise their energy consumption for home heating.

Answer 10

Turning down their heating controls / thermostat could reduce boiler running time.
Closing windows and doors when heating is on could reduce heat loss through openings.

Question 11

define what is meant by U value

Answer 11

The U-value for a particular construction material is the rate at which heat is conducted away through 1m2 of the material for each 1 degree difference in temperature between the outside and the inside of the building