Coursework Assignment

| December 7, 2015

Coursework Assignment

School of the Built Environment and Architecture

Introduction to Building Services Engineering (BEA_4_455).
Design a House

Aim
This assignment is intended to integrate and extend work from the lecture based material of the Introduction to Building Services Engineering module by application to a design project.

Learning Outcomes

This assignment must demonstrate:
• A critical appraisal of the topics given in lectures
• An understanding of heat loss and building systems principles
• Clear communication skills
• A professional standard of formal writing

Assignment Requirements.

You are asked to design the heating, hot water, and ventilation and systems for a three bedroom house. You are given the building details and a description of the occupants/usage patterns.

1) Heating system:

This home will use a gas fed boiler and LTHW radiator system for heating. Preliminary heat loss calculations have been carried out. Given these values, you are tasked with sizing the boiler, the radiators, selecting their locations, and laying out the pipework. Consider the location of incoming gas when choosing your boiler location.

2) Hot water:

You are tasked with ensuring that there will be sufficient hot water to accommodate the needs of the family described in the details below. First consider whether the hot water should be supplied by the gas boiler that is feeding the LTHW radiator system, or point of use electric heating? Should you assume a calorifier or storage tank, and what would be the space requirements for this design decision? How do these factors impact your selection of the boiler for question 1.

3) Ventilation:

The space must comply with Building Regulations Part F, and ensure adequate ventilation. Determine what these ventilation requirements are, and whether this can be met through natural ventilation or whether a mechanical ventilation system is needed? Consider the size implications of a mechanical ventilation system and the ductwork requirements. Would local extracts in the bathroom and kitchen be sufficient?

4) Passivhaus design alternatives:

Finally, the client is curious how the above calculations would change if the home were designed to Passivhaus standard. Using the description of Passivhaus provided below, recalculate the heat loss according to the method shown and discuss the implications that these new heat loss values would have for your heating system sizing in question 1.

• You must keep a copy of the submitted report since your report may not be returned to you.

Submission Deadline: Thursday 14thJanuary 2016

Building Details:
The design calls for a two storey, 3 bedroom detached house, which will be occupied by a family of four: two parents, and two teenage children.
The 1950’s home has an uninsulated flat roof, with no additional loft space above.
The room heights are all 3m, floor and wall thicknesses may be ignored in any calculations.
All windows are equally sized at 1.5m2, the external door is 2m2.

Design Conditions:
Location: London
External design temperature: -4°C
Internal design temperature: 20°C
Infiltration: 2 ach
Thermal Elements:
Total Area
[m2] U-value
[W/m2K]
Wall 128.5 1.5
Ground floor 37.5 1.5
Roof 37.5 1.5
Window 19.5 6.0
Doors 2 3.0
Problem 1: Heating system
You are tasked with designing the heating system. The first step is calculating the heat loss from the home. This has been done for you using the following method:
Heat loss calculations depend on heat loss (Q) through both the fabric (Qf) and the ventilation (Qv).
(Equation 1)

Fabric heat loss, i.e. heat loss thought walls, doors, windows, roof and floor is given by:
(Equation 2)
where: Qf is the fabric heat loss [W]
A is the area of an element of the structure of the building [m2]
U is the thermal transmittance of the structural element [W/m2K]
ti- to is the temperature difference from inside to outside [oC]

NOTE: fabric heat loss Qfis needed for each thermal element: walls, floor, roof, windows, doors. So in order to calculate the fabric heat loss, we need the area and U-value of each thermal element.
Next, we need the temperature difference ti-to.Here ti = 20 oC and to = -4 oC, thus (ti-to) = ?t = 24 oC throughout the calculation.

Finally, insert these into Equation 2 for each thermal element. This is given in the following table:
A
[m2] U
[W/m2K] (ti-to)
[K] Qf
[W]
Wall 128.5 1.5 24
Ground floor 37.5 1.5 24
Roof 37.5 1.5 24
Window 19.5 6.0 24
Doors 2 3.0 24
Total Fabric Heat Loss (Qf)

The total heat lost through the fabric of the home (Qf) is therefore ____ kW. Next we need to determine the heat lost through the ventilation/infiltration.
Ventilation / infiltration heat loss resulting from the air exchange between the inside and the outside is given by:
(Equation 3)
where: Qv is the ventilation heat loss [W]
N is the infiltration rate in air changes per hour [ach]
V is the volume of the space [m3]
ti- to is the temperature difference from inside to outside [oC]

Using equation 3, the ventilation heat loss calculated from the building info above is:
infiltration 2 ach
Volume 225 m3
(ti-to) 24°C
Qv

Thus the total ventilation heat loss is: Qv = ____ kW
The total heat loss is: Q = Qf + Qv
Q = ___kW + ___ kW
Q = ___ kW

You now have the total heat loss from your home. Using this heat loss, carry out the following tasks:
1. Complete the table/blanks above and determine the total heat loss for the home.
2. Size a boiler that can meet this heating demand and decide where it should be located in the home. Assume a suitable design margin. Specifically note the location of the flu and how this was considered in your selection of a suitable boiler location.
3. You have decided that you need 8 radiators to heat the home, four downstairs and four upstairs. Determine the size of the radiators needed for each room. You may assume each room (and thus each radiator) is the same size for the purposes of this exercise.
4. Chose the locations of your 8 radiators and lay out the pipework leading to and from each radiator. Consider the direction of the floor boards in your decisions.
Problem 2: Hot water system design:
Hot Water Requirements:
Typical hot water use for a family of four = 150 L/day
Energy use for hot water for family of four = 20 MJ/day
You are tasked with designing the hot water system for this home. Consider the following, and justify your choices:
1. Assume that at peak the shower and kitchen faucet are both in use (9 L/min and 4 L/min respectively). Determine the peak energy use required for hot water.
2. Decide whether the hot water should be supplied by the gas boiler that is feeding the LTHW radiator system, or point of use electric heating?
3. Should you assume a calorifier or storage tank, and what would be the space requirements for this design decision?
4. How do these factors impact your selection of the boiler for question 1.

Problem 3: Ventilation system design:
Ventilation Requirements:
Minimum fresh air rate = 8 l/s/person.
For bathrooms it is 15 l/s for intermittent use
For kitchens it is 30 l/s for intermittent use
You are tasked with designing the ventilation system for this home. Consider the following, and justify your choices:
1. If you were to install local extracts in the kitchen and bathroom, what size would they have to be to deliver the minimum fresh air rate required?
2. Using the drawings above show a potential layout for the ductwork of a balanced supply and extract ventilation system. Discuss the space requirements for the ductwork. Assume that a Brookvent AirCycle 1.2 system will be used. (http://www.brookvent.co.uk/heat-recovery-ventilation/aircycle-1-2/)
3. Discuss the pros and cons of each method above. What are the space implications for each approach?

Problem 4: Passivhaus design alternatives
Passivhaus is an energy efficient design standard that requires very low U-values and a low infiltration rate. Given the information below, revisit the heat loss calculation given for Problem 1. Resize your heating system based on this heat loss calculation.
Passivhaus Thermal Elements:
U values
[W/m2K]
Wall 0.10
Ground floor 0.10
Roof 0.10
Window 1.00
Doors 1.00

1. Complete the table below to find the total fabric heat loss (Qf) for a Passivhaus standard U-value home:
Heat Loss Calc (fabric)
A
[m2] U
[W/m2K] (ti-to)
[K] Qf
[W]
Wall 128.5 0.1 24
Ground floor 37.5 0.1 24
Roof 37.5 0.1 24
Window 19.5 1.0 24
Doors 2 1.0 24
Total Fabric Heat Loss (Qf)

2. Next calculate the ventilation heat loss (Qv) for an infiltration rate of 0.03 ach:

Heat Loss Calc (ventilation)
Infiltration (N) 0.03
Volume (V) 225
(ti-to) 24
Qv

3. Now find the total heat loss for the home built to Passivhaus standard:
Q = Qv + Qf
4. Discuss the differences between this total heating load and the heating provided for Problem 1. How would this impact the sizing and selection of your heating system?
5. How would a passivhaus design impact your selection of ventilation system? Would a local extract system be successful, or would a balanced supply and extract system with heat recovery be more effective?

Marking Scheme:

Guidance notes: The framework below will be used for the marking against the standard of the work submitted. The range and depth of this research will influence the grading within the bands shown below.

(0% – 40%) The submitted work shows only a basic understanding of the task and contains significant errors and/or inaccuracies and/or is incomplete.
(40% -60%) The submission addresses the task fully and is largely accurate.
(60% – 70%) The submitted work demonstrates an in depth understanding of the principles involved in
carrying out the tasks.
(70% – 100%) Is awarded for work that might incorporate some/all of the following: independent research to validate your explanations, comparison and contrast of conflicting opinions, discussion of potential ambiguities, critical evaluation of the methodologies and results. Referencing must be accurate.
Referencing Your Work
For a complete description please refer to a copy of the London South Bank University documents Referencing Using the Harvard System and Referencing Electronic Sources available from LRC or over the web at http://www.lisa.lsbu.ac.uk/helpsheets/hs30.pdf and http://www.lisa.lsbu.ac.uk/helpsheets/hs31.pdf
It is most important when listing references and/or compiling a bibliography to record the following, (either on a card index or on a computer file):
For Books
• author’s name and initials;
• title;
• publisher;
• place of publication;
• year of publication;
• chapter and/or page to page numbers;
• ISBN number.

For Articles in journals
• author’s name and initials;
• title of article;
• title of journal (most journals have a recognised abbreviation);
• volume, number, issue, page to page numbers;
• date.
Use a standard format for your references, typically as in these notes. Full details of methods of referencing are given in a handout available from the LRC. For example:
1. LEGG, RC (1999) Notes on Experimentation, Third Edition, South Bank University

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