Developing Energy Efficient Building Design

Introduction

Aims and Objectives

The following five points are the key aims and objectives of the proposed building design:

1. To provide the client with an energy efficient building design.
2. To utilise renewable energy systems to reduce the buildings carbon footprint.
3. To use materials in the construction of the building fabric that minimise heat losses/gains so as to reduce the loads on the services systems, and therefore the energy consumption.
4. To provide a flexible, ‘let able’ HVAC system solution for the landlord/tenant.
5. To provide a design solution in accordance with current Building Regulations.

Building summary

Heron Tower is an office block located in Central London near to Liverpool Street train station. The site is situated on a traffic island bordered by Camomile Street, Outwich Street and Bishopsgate. The building has a footprint of approximately 1610m2.

Site Location

Heron Tower is a lightweight steel frame construction, with a concrete structural slab. The external façade of the building is predominantly glazed. The building consists of a basement level, Ground Floor and 2 Floors above ground. The basement will predominantly be used for plant and storage. The ground floor comprises an entrance lobby / reception area, retail area and a loading bay. Each of the floors above ground will be broken down into two distinct areas, the office area and the core area. The building has a flat roof that is available for use for plant and equipment.

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The office area is to be let to tenants and will be open plan, with a floor area of approximately 1270m2. The core area will be under the control of the building landlord and will house the lifts, stairs, toilets, service risers and will have an allowance for space for tenants’ plant. The core area has a floor area of approximately 340m2. The total floor area is therefore approximately 6440m2, of which 3900m2 is designated landlords space (i.e. plant, storage, services, retail etc.), and 2540m2 to be let.

Occupancy

Design Criteria

Alert the reading where you’re getting the information to design each room of the building, what standards you are trying to meet / exceed.

From experience, this is best presented as a cut down of an Excel in the appendix in the form of a table. This sheet should have criteria for every room. Cut it down to every type of room, so it fits on one page, usually rotated, tricky.

Environmental data from CIBSE Guide A [2] 

Lighting data from CIBSE LG7 -Lighting for Offices [3] 

Ventilation

Cooling

Heating

Domestic Cold Water

The domestic cold water service will be provided via a cold water booster set, taking water from a mains fed storage tank. This service will provide water for drinking, toilets, cleaning, mechanical pressurisation units, and will also feed the domestic hot water system via an unvented storage calorifier. The cold water service will be sized as follows:

Occupancy:

Cold water demand:

Hot water demand:

Domestic Hot Water

The domestic hot water service will be provided via a two-pipe system fed from a central unvented storage calorifier, with a system pump to circulate the water to maintain the temperature. It is proposed that the primary method of heating the water is produced using an indirect solar hot water heating system.

The system will comprise a solar array on the roof of the building that will heat the domestic hot water via a coil in the storage calorifier. The system water will be circulated through the solar panels and coil using a pump.

The calorifier provided will have dual coils to allow the solar heating system to be supplemented by the main building heating system. This secondary coil will be used to heat the water if the solar system fails to meet hot water demand. Both coils will be controlled using automatic 3-port control valves

For more detailed information about the solar hot water heating system see section 6.1.

Acoustics

Lighting

Electrical Services

Supplemented by wind turbines on roof

Distribution of Services

Landlord Areas

Mechanical

Electrical

Tenants / Public Areas

Mechanical

LTHW and CHW pipework to air conditioning units will be housed in the ceiling void.

Electrical

Distribution of small power to the office area will be via floor boxes fed from a raised floor. Power for air conditioning units and lighting will be distributed via the ceiling void.

Energy Metering

Metering will be provided on both incoming service mains to the site and on sub-circuits within the building for monitoring by the building energy manager. Metering provisions will enable the energy manager to attribute at least 90% of the energy usage to specific systems, e.g. lighting, heating etc. in accordance with The Building Regulations Part L2A [4] . The meters provided shall be BMS compatible to allow for automatic data collection. The metering strategy for the building is as follows:

Mains Metering

Electricity

Electricity will be metered on the incoming mains to monitor the buildings overall electrical energy usage and for billing purposes (in accordance with ??)

Water

Water will be metered on the incoming mains to monitor the overall water usage and for billing purposes (in accordance with water bylaws).

Gas

Gas will be metered on the incoming mains to monitor the overall gas usage and for billing purposes (in accordance with ??)

Sub-Metering

Sub-metering will be provided to monitor energy usage on sub-systems so that the overall energy usage of the building can be broken down into the various systems and analysed by the building energy manager. Sub-metering will also be used to differentiate between energy usage by the landlord and tenants for billing purposes. The sub-metering strategy has been devised in accordance with CIBSE TM39 [5] . The sub-metering strategy for the building is as follows:

Electricity

The landlords and tenants supplies will be fed from separate distribution boards to allow differentiation between energy usages. The feeds to these distribution boards will be metered at the L.V switchgear. Metering will also be provided at the local distribution boards to monitor energy usage across the main categories of electricity usage. The categories that will be monitored are:

• Lighting
• Office small power (including computer equipment etc.)
• Ventilation plant
• Heating plant
• Cooling plant
• Air conditioning units

Heating/Air Conditioning

Heating and air conditioning in the landlord and tenant areas will be fed by separate sub-circuits. The energy used by each of these circuits will be monitored by using in line pipe heat meters located in the service risers.

Water

Domestic hot and cold water usage at the toilets on levels 1 & 2, and in the staff areas in the basement will be monitored using water meters located in the service risers.

Gas

Gas is only used for the gas fired boiler plant. As the gas is metered at the incoming main no sub-metering is required.

Solar Domestic Hot Water System

The output of the solar hot water generation system will be measured by installing a heat meter inline to the feed from the solar array to the storage calorifier. This heat meter will measure the flow rate of the water as well as its temperature in order to gauge system output. A meter will also be installed in the sub-circuit feed from the LTHW system to ascertain how much LTHW has to be used when the solar hot water generation system fails to satisfy demand.

Wind Power System

Energy produced by the wind turbines located on the roof of the building will be metered to provide the building energy manager with data on the actual output of the wind turbines. This will be metered on the common feed from the turbines to the storage battery.

The consultation on changes to the technical guidance for Part L issued in June 2009 proposes:

The output of ‘any renewable energy system provided as part of the works’ must be separately monitored.

Safety

Benchmarking

This section is to give the reader an idea of the minimum standard to be achieved by your proposed design. Usually BSRIA Rule of Thumb gives you a starting point in W/m2. There is usually guidance in the form of Best Practice for a particular type of building: school, hospital, office, leisure centre etc.

CIBSE guide A

Table 6.2 Benchmark allowances for internal heat gains in typical buildings

BSRIA Rules of thumb 4th ed

Heat Calculations

You will need to calculate the current baseline design using typical construction materials. This could be done using Hevacomp [6] , IES [7] or Excel. Then you could consider orientation, shading and construction materials to recalculate heat loss /gains. Typically, improved U values for windows are considered, but then you must justify the decision based on costs / environmental pollution etc.

Could include the unoptimised design, if the building is a refurbishment. You should include any restrictions, listed building, planning constraints etc.

Heat losses

You should make the calculations, say in Hevacomp, but only include a summary in the text. This includes the U values for the building elements: wall, floor, roof, door, windows, these could be calculated from scratch, taken from the CIBSE guide, Hevacomp database or manufacturer’s data.

Literature Review (In-depth investigation)

The literature review should consider one or two particular areas. You should use a selection matrix to highlight two or three potential solutions depending on your criteria (your client usually wants the cheapest construction- low capital cost) usually you want either low C02, low energy bills, low maintenance, highest safety etc. You must be able to defend your selection.

Now investigate the options based on the selection matrix, you don’t need to supply manufacture information, but you may need to hassle manufacturer’s for cost information, or size information (e.g bore hole depths for ground source heat pumps, GSHP)

Heating supply for example

You could select gas or electric or CHP or GSHP or ASHP or oil, liquefied gas etc. Select two or three and investigate options in-depth

Heating systems

You could decide between radiators, under-floor heating, electric storage heaters etc.

Ventilation Requirements

Ventilation is a means of changing the air within a space in order to:

• Provide fresh air for respiration
• Preserve oxygen levels in the air in enclosed spaces
• Control carbon dioxide
• Control moisture/humidity
• Remove heat from processes carried out within a space
• Remove atmospheric contaminants such as odours, smoke and dust
• Maintain comfort conditions
• Provide oxygen for combustion

Types of Ventilation

Ventilation may take many forms and the method of ventilating buildings will vary from project to project. Whatever the specific design for ventilating a building may be, it can always be divided into three categories- natural ventilation, mechanical ventilation and air conditioning. Designers may decide to focus the design of the buildings ventilation system solely on one of these three methods, or to use a combination of the three.

Natural Ventilation

Natural ventilation is the most economic method of ventilating a building as it uses components of the buildings structure, such as windows, louvres, trickle vents and air bricks to provide the buildings ventilation, therefore requiring little or no energy to operate (although it can contribute to the buildings energy losses).

When deciding to use natural ventilation in a building design the following factors should be taken into consideration:

• Location: is the building situated in an area where having windows open for the purpose of ventilation is going to allow high noise levels or smells into the building?
• Size: how big is the building? If the building is large are there internal rooms that are not close to external walls/windows and could therefore be insufficiently ventilated naturally?
• Temperature maintenance: what measures will be used to maintain a comfortable internal temperature if the external temperatures are fluctuating?
• Energy consumption: although utilising natural ventilation will reduce energy consumption by not requiring any mechanical plant to operate, constantly having windows open will lead to larger heat losses than would be expected from an identical sealed building. This will increase the energy use of any heating systems in place.
• Seasonal weather: will natural ventilation provide enough cooling on hot summer’s days to maintain comfortable conditions? Will it still be practical to have windows open on particularly cold days?

If natural ventilation is used as a buildings sole means of ventilation then it can be very difficult to maintain comfortable conditions all year round, as you are depending on an unknown and uncontrollable factor i.e. the weather. The only control that is really available is to open or close windows or other building components.

Mechanical Ventilation

Mechanical ventilation systems are installed where natural ventilation is impractical or there is a necessity to achieve a specific number of air changes per hour in order to comply with legislation and regulations. Mechanical ventilation systems can take three forms:

1. Mechanical intake with natural extract
2. Mechanical extract with natural intake
3. Mechanical intake and extract

Whilst both the capital and running costs of a mechanical system are higher than that of a natural system, mechanical systems will provide a reliable and controllable air change rate that is required in some circumstances, and is simply not achievable via natural ventilation.

When deciding to use mechanical ventilation in a building design the following factors should be taken into consideration:

• Size: is the building big enough to warrant the installation of a mechanical ventilation system?
• Location/use of rooms: does the building have internal rooms that have no other means of smell/heat extraction such as toilets or kitchens, therefore requiring a mechanical ventilation system?
• Cost: does the building’s need for ventilation warrant the cost of installing, running and maintaining a mechanical ventilation system?
• Maintenance: is maintenance of the system going to be easy and affordable?
• Space: is there going to be enough space in the building for the plant/distribution systems required for a mechanical ventilation system?

A mechanical ventilation system provides the occupants of the building with a higher level of control over comfort conditions than would be provided when relying solely on natural ventilation. It would not however provide the level of controllability that can be achieved by an air conditioning system.

Air Conditioning

Air conditioning is the process of controlling condition of the air supplied to a space by subjecting the air to a number of processes including heating, cooling, humidification and dehumidification. Air conditioning is used where close control of comfort conditions is required, or where acceptable internal conditions cannot be achieved using either natural or mechanical ventilation.

When deciding to use an air conditioning system in a building design the following factors should be taken into consideration:

• Size: is the building big enough to warrant the installation of an air conditioning system?
• Location/use of rooms: does the building have internal rooms that have no other means of smell/heat extraction such as toilets or kitchens, therefore requiring the installation of a mechanical ventilation system as well as the air conditioning system?
• Cost: is the need to maintain comfort conditions and temperatures great enough to warrant the cost of installing, running and maintaining an air-conditioning system?
• Maintenance: is maintenance of the system going to be easy and affordable?
• Space: is there going to be enough space in the building for the plant/distribution systems required for an air conditioning system?
• Efficiency: is the plant that is going to be installed going to be energy efficient?

An air conditioning system gives by far the greatest level of control over comfort conditions. Temperatures can be controlled locally and accurately, meaning that people in different areas of the building can decide on the conditions that they feel most comfortable. The installation of an air conditioning system can also remove the requirement for a separate heating system, if a multi-functional fan coil unit system, or equivalent, were to be installed, therefore allowing conditions to be maintained comfortably all year round.

Renewables

Now the Mayor of London has put his backing into renewables, it must be included as a potential measure.

Typically students investigate hydrogen, solar heated water, PV, tidal, wind or biomass. You need to decide which one is appropriate then make some calculations. Please learn to use equation editor (its under Insert -> Object). Unfortunately, its not installed by default by Word, but you can add it in by a add/remove option in Office Setup.

From your decisions you should be able to calculate the CO2 and energy savings, based this upon a standard condensing boiler and the current price of gas and electricity. Include grants / tax breaks into the calculation.

Finally, financials including simple pay back period should be included, but you should rerun the calculation based on future energy prices as well.