FAQs
Below are some questions we are asked on a frequent basis. If you don’t find the answers you are looking for, then please do not hesitate in contacting us on 01698 373 305 or email: info@powerwall.co.uk
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Q. What were the reasons behind Powerwall developing an off-site volumetric construction system?
We initially designed a volumetric system to look at improving the quality and effectiveness of construction against traditional methods. Our philosophy was to be able to provide a solution which was not limited to rigid shape etc. – what we have is a system which will be able to interpret directly from the architects drawing. We therefore can construct angles and curved features as well as flexibility in length width and height of the sections.
The slide below shows how we present this to clients – note the angles in one of the frames as an example of this flexibility.
Q. What do you think are merits and demerits of a volumetric construction system in general?
Our experience is that we can achieve higher levels of quality and performance in key areas such as thermal and acoustic specifications and still maintain a cost effective solution. The speed of construction is also of considerable benefit to many end users. We produce a very high quality permanent structure with a lifespan of 200 years and a design life of 60 years.
One of the downsides in the UK is still the slow acceptance for this type of system – this is more a cultural issue than one of technology. The good news for us is that this is changing very quickly.
In other markets that we are involved in such as the Middle East, Sweden, Holland, Germany and USA/Canada and Japan – there is increasingly more acceptance of the technology and so less resistance.
Q. Powerwall Space Frame Systems figures indicate build/construction costs are 10 to 15% lower than conventional build.” What are the major contributing factors?
The cost benefits are achieved through a number of key areas;
Time saving for the construction phase
Reduced material costs through minimized wastage
Reduced snagging and retrofit costs on site – we get it right first time
Prelims and foundation costs for our system are also very much lower due to the design of the system requiring reduced foundations.
Q. What is the minimum number of volumetric frame units (modules) to be produced to achieve the “10 to 15% lower” cost advantage?
We are cost competitive on one off builds – most of our work tends to be on varied projects rather than long production runs of similar units. Therefore our cost savings are based on this varied production output – which we would see as the worst case scenario. We have recently started to work on more standardized projects and optimized designs for some of our clients (such as affordable homes for government housing) and we are seeing further cost benefits in this area of a further 10% benefit.
Q. You say the steel frame is accurate to +/- 1mm. Does it mean the accuracy refers to width, depth and length? How do you ensure the accuracy on the production/assembly line?
The accuracy does refer to width depth and length (and indeed can be achieved over the frame diagonal). A typical frame size for us is 3.8mx3.1mx10m. (WxHxL)
At the heart of our production process is the construction of the structural frame. We use a rotating jig (which is accurately calibrated) to form the structural frame element and it is the use of this jig which allows us to achieve the +/- 1 mm tolerance.
The picture below is the frame being set up on the jig and then rotated. The rotational aspect allows us to work at ground/working height for elements of the fabrication and construction.
Q. Are there any rules regarding module arrangements?
The system has great flexibility , however we do have some guides (or rules) relating to effective and efficient design – such as careful orientation of the frames to reduce the number of frames in any one structure (cost savings). Obviously the position of any down columns and how these would fit within a building design such as the position of walls and windows and doors for example.
Q. How do you conduct structural verification for each building?
We complete a full structural analysis for each building.
An initial preliminary design is performed using past experience in similar jobs where the design loads are determined, the pod layout is defined and the preliminary sizes of steel are defined. That information is then used as input for a Finite Element Software where the building is modelled, the forces are obtained and the building is designed according to the relevant standard and regulations.
Q. We understand that your system is applicable to detached single-family homes and range of buildings up to 22-story buildings. Except for the sizes of posts and beams, what basic changes are necessary depending on the structure?
The main changes are related to the size of the posts and beams in terms of structural loading.
Depending on the structures characteristics the structural steel frames are designed accordingly. For medium to high rise buildings the cross section dimensions of the columns should be increased and additional bracing is required, this lateral resisting system can be achieved either by a concrete core or by an external bracing system.
The increase of the columns sizes, a consequence of the higher vertical and horizontal loads, will also result in a redesign of the Powerwall connector, making with wider and deeper. In the same way the base plates should be more robust and the threaded steel rod should also be increased.
Q. How do you ensure air-tightness performance in terms of module-to-module connections, wall installation and window installation?
The modular frame is enveloped in insulation, vapour control layers and surface finish materials to create a staggered material overlap and warm frame construction with all respective layers being sealed at their independent joints. This prevents direct air path leakage. All air voids are foam injected around window & door openings and thermal bridging details are adopted at all openings to prevent straight through joints.
Q. Do your volumetric system products require any “special” organizational system to sell and construct them?
No we tend to operate our sales in a conventional manner and compete for jobs based on performance and cost parameters. We do use specific software that we have designed to assist us in providing quick and accurate costs and this information provides additional data input information for design.
We also use local supplied materials for the build process in excess of 95% of the bill of materials. (the connectors are the key element we specific to be purchased in order to control quality of this key component – we do not sell this as a highly marked up cost element – we do this more for control of quality and knowledge of quantity built – part of our license model).
We have a very efficient installation process and tend to operate at 10 frames per day on site erection with a team of 4 men and 1 supervisor.
Q. How many “volumetric system” detached single-family homes do you build a year?
We build a number of different types of buildings (Homes, Schools, Health Centres, Hotels etc.) in any year including detached family homes. Our capacity for build is set by our production capacity and typically we are producing 20,000 to 30,000 sqm/year.
Family homes account for around +60% of our production capacity.
Q. Is it possible to combine your system with other construction systems?
Yes.
We are often involved in projects which have a mixture of other construction systems where we offer part of the solution. In some recent examples we are building apartments on top of other existing buildings in key city centre locations.
Q. Do you have “standard or basic” module sizes? If so, what are their dimensions? Do you have any special rules to put modules together to build a house or multi-story building?
We do not have any special standard sizes – this is because our system is designed to meet the architect’s drawings.
However we do try and use simple rules to achieve efficient build principals, such as;
• Size of units for cost effective structural efficiency
• Size of units for cost effective transport
• Size and shape of units to minimize the number of sections within a design (reduce cost etc.)
Our average size of section that generally meets these guidelines for cost and performance is (WxHxL) 3.8m x 3.1m x 10m. Typically for us a 150 square meter building would have 4 to 6 sections (depending on design).
There are rules about putting modules together – but these tend to be considered guiding principles for efficient design and cost. We can have features such as overhangs etc.
Q. Do you have “standard or basic” design details for specific applications?
We do have a library of specific details and solutions to many different types of building applications. These include elements such as concrete floors, air conditioning applications and specific external finishes etc. As the system has flexibility we continue to develop these on an ongoing basis and work with our clients and partners to provide these solutions as required.
Q. What do you use for subfloors? Formed concrete or some sort of screw-down planking?
We generally supply what the client is looking for – the system has been designed to have a great deal of flexibility.
• The most popular offering is a lightweight steel joist system sub floor with the timber flooring etc on top.
• We also offer a SIP type (we call it PIP Powerwall Insulated Panel) sub floor – and as above the required flooring on top.
• We in some cases offer a concrete floor – This tends to be the lightweight steel joist system supporting a rib and the concrete screed onto this.
• In some cases the rib is used without a subfloor and then screeded etc. – it depends on design loadings etc.
Our ceilings on the lower modules and floors on the one above (and so on all the way up) are separate – we generally work with a standard gap (40mm) separation – although for many jobs there can be a greater gap or void depending on the clients specification (service space for example).
Q. What do completed module weigh per sq foot or meter? I’m trying to compare the system to our very heavy duty materials?
The system is flexible and each module configuration is to the client job.
A typical module size of around WxLxH of 3.6m x 8m x 3.1m would be between 5 to 7 Tonnes – this would depend on the level of internal detail and fit out (bathrooms, kitchens internal walling).
Therefore typically our system is around 180kg/m2 to 240kg/m2 module weight (fitted out).
Our external Wall (infill) is either 257mm or 207 mm (depends on structure specification) – the weight of the infill wall is around 35kg/m2.
Q. Do you install your exterior finishes to the modules in the factory? How do you seam the EIFS? Your photos look seamless?
We use a Drainable Honeycomb Panel as an external panel on the modules. This then has an adhesive coat applied (and we can take it to this stage in the factory) – on top of this is the application of external finish such as Stucco or brick or stone cladding etc. We always do the final finish on site as we do not want the buildings to look modular.
The honeycomb panel is an aluminum honeycomb sandwiched between two GRP faces. The panel when applied on the module is butt jointed and taped (seamed) with the same GRP material – This gives what we say is a monolithic panel and the reason that we can have this seamless solution.
Q. Do you typically sell you modules as “turn-key” from the sill-plate up or are they finished on site by the General Contractor?
Generally we do sell as turnkey and finish on site ourselves. Again flexibility and the construction sector practices mean that sometimes we have a general contractor do more on site finishing. This is less common for us.
Q. Who are the key clients ?
Our key clients are fairly wide spectrum of organisations. Our approach to contracts and therefore how we interface with the client varies, – in some cases we take on the main contractor role – in other cases we are part of the construction supply chain as a sub-contracting element – it depends on the job. Examples are
• Direct clients such as Hotel developers
• Housing associations (government housing)
• Local government on Education or health care projects
• Main contractors on specific projects
We also have relationships with key influencers such as Architects who will specify our system – with the client or main contractor then using our system.
Q. Are you also open to sell your items in specific markes directly without using a local manufacturing partner? Do you think that it is possible to achieve competitive costs compared to conventional construction with the need to ship the modules from Scotland?
We have done some projects where we have manufactured the buildings in our own plant and shipped from Scotland. There are additional costs for transport, and so these projects need to be looked at carefully. Our main business approach is to work with local partners under a license model and therefore the end client can often benefit from local labour rates and material costs as well as lower transport costs.
Q. How do the costs of construction of your system compare in our market against your UK costs? Can you provide some examples please?
We find we are competitive in the UK and other markets in Northern Europe. It depends on labour costs and material costs.
We have developed a really simple quick way to try to get a simple comparison. We have utilised as simple optimised design for a 3 Bedroom home as the baseline comparator. It requires you to input a few basic details of local rates and materials such as steel cost and doors windows and plasterboard. The result will be a very rough comparison for the local costs against our UK costs for this design. It then should be a guide for other buildings. We can supply this if requested.
Our experience and discussions with existing Licenses and other construction companies around the world is that the figures when local values are substituted our system is highly competitive.
The accurate way is to look at a full Bill of Quantities for a specific design and then substitute the local figures into this. This is obviously more time consuming.
Q. Can you give some evidence of the lower costs of construction of your system in different markets.
We have looked at some general costs in the Middle East (using Saudi Arabia KSA as a baseline)- the results below indicate the cost differential against UK (and Western Europe)
Q. How do the costs of construction of your system breakdown against the key elements such as key materials, labour and transport.
The following pie chart is a typical cost breakdown for low cost accommodation/budget hotel/student accommodation, and shows the general trend. Each project is different depending on design and fit out levels but again this can give an approximation.
Q. Main raw materials and quantity to be purchased in other country
95% of the materials can be sourced locally in other countries – this is one of the key elements of our system design to ensure that there is an easy set up and ongoing material supply in the international markets that we license our technology to.
• Structural Steel Tube – Grades S275/S355
• Slit steel coils BS EN 10346:2009- S350GD+Z275-M-A-C
• Insulation Materials Rockwool and Glass-wool
• Timber or Orientated Strand Board (OSB)
A variety of other construction materials such as;
• Plasterboard, Electrical cabling and plumbing pipes (copper and plastic)
• There are also additional items such as Doors & Windows and bathrooms and kitchens.
Calculated weights based on average Pod 8mx3.8mx3.1m with Floor + Ceiling+ 2xExternal Walls +1xInternal wall is noted below;
• Structural Steel 1850kg/Average Pod
• Lightweight Steel 950kg/Average Pod
• Fibre Insulation 565 kg/Pod
• Plaster Board 875 kg/Pod
Average weight of a finished module is 6 tonnes
Average module is 30 sqm for this excercise
1xmodule/jig per 8 hour shift
You can multiply this up by number of jigs and number of shifts to get an approximate answer.
Q. What Raw materials and quantity need to be imported
As stated 95% of materials will be locally sourced – the following elements will be supplied by Powerwall;
Connectors: Powerwall manage and supply the connectors as these are a critical component and we need to ensure the highest quality of this product. It is manufactured from cast steel – Over time we would look to find an approved local or regional hub supplier.
HoneyComb Panel: Powerwall produce a drainable Honeycomb panel which is unique to Powerwall and this is manufactured in our plant in Italy. It is manufactured from Aluminium and Glass Reinforced Resin. Again over time we would look to seek out local or regional partners to manufacture this for us or to set up a technology license for manufacture
Q. What size of facility do I need to produce modular units?
The size of facility depends on your required capacity. Our system utilises some key manufacturing tooling or jigs. The very rough figures for a green field development are;
Output Capacity of Plant /annum *
Size of Facility required
2 Jigs = output of 250,000 sqft (or 25,000 sqm)
50,000 sqft ( or 5,000 sqm)
4 Jigs = 500,000 sqft (or 50,000 sqm)
100,000 sqft (or 10,000 sqm)
* Single 8hr shift model – increased capacity if double or triple shift.
We can provide more detailed information including factory layout guidelines and labour requirements as required.
Q. What sort of market size would an individual Licensee or Licensee plant have? Would it be measured in sq. Miles, population etc.?
There are a number of factors that we use as a guide;
• Typically 300m radius for transport – this is a UK figure and some markets this will be a little greater.
• Our experience suggests; 1 Licensee/5m to 10m population (this depends on overall density)
Q. What sort of specialist equipment or tooling is involved or required?
There are some very specific pieces of tooling required such as;
• The rotating jigs (Powerwall design) for the structural frame fabrication.
• The in-fill panels require either industry standard lightweight steel rolling mills or SIP panel production equipment (Powerwall design).
• Some specific basic bespoke tooling such as stands, moving wheels etc.
• Standard equipment such as welding rigs, forklifts (overhead crane options), general hand tools.
A Licensee partner is provided with the required equipment lists for the standard tooling, Powerwall can provide the bespoke items.
Q. What are the main energy consuming processes or equipment in the process?
The processes or equipment used are not heavy on energy use – the key equipment and tooling required is;
• Welding Equipment for the manufacture of the structural steel frames.
• Lightweight Steel Rolling Mill Machines
• Structural Insulated Panel Press
Q. What potential environmental pollution issues would be caused by the plant?
The process is designed to impact positively with comparison to traditional on site construction methods.
• Limited waste typically 5% – recycle of most materials with some limited landfill disposal. We are also trying to reduce packaging waste materials as part of an ongoing programme.
• 36% less embodied energy than traditional build.
Our processes use little or no hazardous materials, and where we use products such as paint or protective coatings these tend to be water based
Q. What sort of design side software is involved or required?
There are a number of software packages that we use – but at the heart of the system is 3D Cad software such as AutoCad. There are also other software modules to assist in manufacture and of course importantly up front is the estimating and costing package. A basic explanation of the software packages and their use is as follows;
• Estimating & Costing Software [Powerwall Package] – we use this to estimate the job (steel sizes and costs, plasterboard and honeycomb sqm etc and number and arrangement of pods etc). The output is also dimensionally sound and the basic information is then sent on to the design packages.
• Detail Design [3D product such as AutoCad] – we use the supplied data from the architect and interpret this to our design interpretation. We would use the previous output pod overlay to assist us- so this is an efficiency gain. It is the detail aspect of particular jobs that require the 3D flexibility.
• Panel Design [ we can use AutoCad or Vertex – this is more a dedicated product to the panel design and for framing] – the decision is made by our design team as to what is the most flexible and more efficient route for each job.
• Panel Manufacturing [GCad and Scottsdale Rolling Mill software] – we use this package to produce the manufacturing data and then produce the direct cutting list data for the rolling mills panels for each element.
