Construction Tech & Environmental Services

Question 1

What types of lifts are available?

Answer 1

Generally lifts can be divided into two types:
- Hydraulic
- Electric
* Electric lifts have two subsets, geared and gearless (Machine Roomless)

Question 2

How do Electric lifts work?

Answer 2

Electric lifts work with high tensile steel topes which then travel over grooved traction sheaves and pulleys to move the lift up and down.
Counterweights are used on the other end of the steel rope to balance out the weight and to reduce the load on the electric motor driving the traction sheave.
The lift car runs along guide rails in the lift shaft to keep it stable.

Example of electric lift pulley systems

Question 3

What is the difference between Geared and Gearless (MRL) lifts? Can you explain the benefits and disadvantages?

Answer 3

Geared lifts have gears and require a machine room to house their much larger traction machines. They are slower and less expensive than gearless systems. Geared lift motors require oil and more frequent maintenance because of this. The machine room needs to be directly above the lift shaft and so can mean a reduction of usuable roof space. Machine rooms also need to be air conditioned and be of a considerable size. Can travel higher distance - up to 210m

Gearless systems can be situated in the top of a lift shaft, thus not requiring a seperate machine room. They can achieve higher speeds. Gearless systems also have a smoother operation owing to not having gears. They are also more energy efficient and make less noice. Gearless systems are not able to travel as far and are generally limited to 75m.

Geared and Gearless Traction motors

Question 4

Explain How Hydraulic lifts work. What advantages and disadvantages do they have?

Answer 4

Hydraulic lifts work through a pump pushing hydraulic fluid through a cylinder which then actuates a ram. This in turn acts on the lift car from underneath, pushing it up and down as required. Each lift has its own pumping unit and controller, usually situated at the lowest level served no more than 10m from the shaft

Benefits - Simple system, doesnt rely on shaft to bear weight as hydraulic lifts carry the weight directly to the ground. Construction and installation is considerable less expensive than a comparable electric lift installation. Maintenance is cheaper as this is a much simpler system with less moving parts than the electric lift.

Disadvantages - Limited to max of 21m travel (5-6 storeys), louder than electric lifts. Requires a machine room. Hydraulic leaks possible. Less energy efficient than MRL solution.

Hydraulic lift section

Hydraulic lifts have a theoretical maximum travel distance of 21m vertically. This limits them to four or five storeys.

Question 5

What considerations would you make when advising on lift choice?

Answer 5

I would consider the layout of the building, as well as the clients budget and requirements in terms of occupancy.
For Ralph Lauren Paris, I advised to replace the existing lift with a new hydraulic lift, as this was significantly cheaper, would allow utilisaton of the existing machine room at the lowest level and would cause the least disruption.

Question 6

Passivhaus

Explain what Passivhaus is

Answer 6

Passivhaus is a sustainability measure that takes a fabric first approach. Air leakage and heat loss are minimised to levels much lower than seen within the building regulation, and Mechanical ventilation with highly efficient heat recovery is installed to keep the air fresh without losing heat. The idea is, this building is mostly heated by solar gain with minimal need for heating, and where heat is provided it will be from a renewable source and will be kept within the building.

Question 7

What are the levels of Passivhaus, and how are they different?

Answer 7

• Passivhaus Classic - traditional passivhaus, significantly reduces energy use
• Passivhaus Plus - Produces as much energy as occupants comsume. Energy must come from renewable sources and provide enough energy to operate the building throughout the whole year.
• Passivhaus Premium - Produces far more energy than required to operate the building. Over and above standard.

Question 8

What cost uplift might you expect for achieving passivahus standard?

Answer 8

10-15% based on benchmarks.
A cost premium can be attracted from contractors who do not fully understand the requirements and the risks. Other than extra elements such as heat recovery, triple glazing and increased insulation - passivhaus relies on increased workmanship to achieve a high level of air tightness.

Question 9

On the Canning Town project, what elements of construction were affected or generated extra cost to achieve Passivhaus Classic?

Answer 9

External envelope:
- Increased Insulation
- Triple glazed windows
- Extra care on any service penetrations for air tightness
- Much lower tolerances for gaps in insulation in order to meet rigorous air tightness standards
- ‘Thermal bridge free’ construction
MEP
- Mechanical Ventilation with highly efficient heat recovery

In addition to this, a much higher than ususal standard of workmanship is required in the construction delivery.
Additional allowances should be made for frequent air testing as construction progresses, and possible delays and re-work to identify and rectify any air leaks.

Question 10

You mentioned in your summary of experience that a transfer stucture was needed in the ground floor of some of the residential units for retail on the tonbridge town project. Why was this?

Answer 10

The concrete construction for the residential building relies on a grid system which determine column layouts in regular positions on each floor in order to effectively transfer load all the way down to the substructure.
The regular column position did not work with the retail space which required large spaces with as few interruptions as possible. In order to combat this, I allowed for a transfer structure in the 1st floor slab to minimse the incidence of columns.

Question 11

Does Passivhaus apply purely to new build residential?

Answer 11

No, offices, universities and other buildings can achieve this standard.
The EnerPhit standard is also available for retro fit projects which would not be able to meet the passivhaus requirements

Question 12

Who are the AECB?

Answer 12

The Association for Environment Conscious Building

They support the passivhaus trust and other related organisations

Question 13

What are the parts of the building regulations?

Answer 13

Part A: Structure
Part B: Fire safety
Part C: Site preparation and resistance to contaminants and moisture
Part D: Toxic substances
Part E: Resistance to the passage of sound
Part F: Ventilation
Part G: Sanitation, hot water safety and water efficiency
Part H: Drainage and waste disposal
Part J: Heat producing appliances and Fuel storage system
Part K: Protection from falling, collision and impact
Part L: Conservation of fuel and power
Part M: Access to and use of buildings
Part N: Glazing - Safety in relation to impact, opening and cleaning (withdrawn)
Part O: Overheating
Part P: Electrical safety
Part Q: Security - Dwellings
Part R: Physical infrastructure for high-speed electronic communication networks
Part S: Infrastructure for the charging of electric vehicles
Regulation 7: Materials and workmanship

Question 14

What parts of the building Regulations relate to sustainability?

Answer 14

FLOS

Part F: Ventilation
Part L: Conservation of Fuel and Power
Part O: Overheating
Part S: Infrastructure for the charging of electrical vehicles

Question 15

What parts of the building regulations received updates in 2022

Answer 15

FLOS

Part F: Ventilation
* Requirement for trickle vents on new windows

Part L: Conservation of Fuel and Power
* Tightened U values, epecially for timber windows

Part O: Overheating (New)
* Regulation to reduce overheating, especially from solar gain

Part S: Infrastructure for the charging of electrical vehicles (New)
* Introduced requirement for new homes to have infrastructure installed for electric vehicle charging

Question 16

What is substructure?

Answer 16

All elements of work that are undertaken below the damp proof course that provides the basis for the superstructure to be constructed upon.

Question 17

What is the external envelope?

Answer 17

• The materials and components that form the external shell or enclosure of a building.
• These may be load or non-load bearing.

Question 18

What are the Building Regulations?

Answer 18

Legal requirements that set out the minimum performance standards for the design and construction of buildings

Question 19

What are the typical components of site investigations?

Answer 19

Their objective is to collect and record data to help with the design and construction process. This should include matters in relation to the site that may impact the development for example:-
o Boundary hedges & fencing.
o Existing trees.
o Size, depth and location of services including gas, telephone, electricity, water & drains.
o Existing buildings.
o Ground water conditions.
o Soil investigations.
o Trial pit information.

Question 20

What are the main site considerations? (When planning construction works)

Answer 20

• Access
• Storage.
• Accommodation.
• Temporary services.
• Plant.
• Fencing & hoarding.
• Health & Safety risks.

Question 21

What are piles?

Answer 21

• A series of columns constructed or inserted into the ground to transmit the load of a structure to a lower level of subsoil.
• They are used where no suitable foundations conditions are present near ground level or if there is a high water table.

Question 22

What are the different types of piles?

Answer 22

Sheet piles.
Secant piles.
Bored Piles.
Pre-cast piles.
CFA Piles
Contigous Piles

Question 23

What are Sheet Piles?

Answer 23

Sheet piles are sections of sheet materials with interlocking edges that are driven into the ground to provide earth retention and excavation support or to form elements such as basement walls. Sheet piles are most commonly made of steel, but can also be formed of timber or reinforced concrete.

Question 24

What are Secant piles?

Answer 24

Interlocking piles (male and female, often different diameters and hardness) are bored to provide a combination of foundations and basement walls.
o They support in providing a waterproof structure and are often seen when a top down
construction method is used.

Question 25

What are contiguous piles?

Answer 25

Contiguous piles are a series of piles constructed in a line with a gap between them. This can be used to form a retaining wall or to hold back the sides of a deep excavation.
Not waterproof.

Question 26

What are the different ways that the piles transfer their load to the
surrounding ground?

Answer 26

• End bearing piles - transfer load through low bearing capacity soil to a strong stratum such as rock or very dense sand.
• • Friction piles - bear on frictional resistance between their outer surface and the soil in contact.
• • Settlement reducing piles - usually incorporated beneath the central part of a raft foundation in order to reduce differential settlement to an acceptable level.
• • Tension piles - resist uplifting forces that might otherwise cause the structure to be extracted from the ground due to uplifting forces such as hydrostatic pressure, seismic activity or overturning movement.

Question 27

What are the problems to the PQS regarding cost control with piling
and who owns the risk?

Answer 27

The end depth of the piles are never certain and the procurement route used determines who takes the risk.
* For example under a traditional or design & build procurement the main contractor would normally take risk ownership whereas under management contracting the risk would remain with the employer.

Question 28

What is a VAV system?

Answer 28

A Variable Air Volume system is a heating and cooling system that has constant temperatures for each stream but varies the air volume being passed through in order to heat or cool a space.
It will have a local VAV box in each zone, connected to a sensor which will then tell the damper how much air to let through to heat or cool the zone as required.

Question 28

What is a VRF system?

Answer 28

A VRF system keeps constant airflow volumes but instead varies the temp of the air by using refridgerant which cools or heats the air as needed at local zones in FCU’s.
They are much more energy efficient than VAV systems as heating and cooling through the refridgerant is only done as needed.