The priorities of housing design Essay

Materials Recycling Team Research & A ; Coursework



The precedences of lodging design have shifted to high public presentation edifice systems which are efficient, lasting and economically feasible. Materials are need whichrequired to supply high thermic public presentation, comfort and lastingness whilst cut downing waste and cut downing the effects on the environment [ 1 ] . Insulation beds are used in roofs in assorted designs and techniques, in order to battle the different manners of heat transportation that occur in edifices. Two illustrations of loft insularity are polyurethane stiff froth blocks and expanded polystyrene beads, : both of these stuffs are regarded extremely with regard to their public presentation and environmental friendliness whilst both holding their drawbacks. and so within ourWithin this study we will asses each one insulating stuff separately with respects to production methods, in-service considerations and, terminal of life issues, public presentation, design and recycling issues, in order to set up the overall most consequence method of loft insularity.

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2.The Product and Materials: Industry and In-Service:


1 Fabrication and Manufacturing Issues

Polystyrene Bead

Materials Used: Styrene monomer, steam, pentane.First the cinnamene monomer is added to H2O and is put in a reaction boiler with an fomenter. Assorted other chemicals are so added which will impact the suspension of the monomer in H2O and command the polymerised bead growing, molecular weight and other variables necessary to bring forth the coveted merchandise. In the 2nd stage of the procedure, the blowing agent, pentane, is added under force per unit area which impregnates the soft polystyrene beads.

The entire batch rhythm takes a little less than 12 hours. Once the procedure has been completed, the full batch consisting of H2O and the impregnated polystyrene beads is dumped to a de-water system. Following the de-watering procedure, the beads are transferred to driers. The desiccants evaporate the pentane from the beads which is replaced with air. The beads are now up to 40x the original pellet size.

The dried beads are so screened passed through a showing system to supply achieve the coveted size. The screened beads are so packaged, ready for sale.The beads are installed utilizing an air blower, which blows the beads into nothingnesss in the ceilings, which can so be sealed.

Rigid Polyurethane Foam Boards

Materials Used: Polyol, Isocyanate, Aluminium foil.Polyurethane froth was foremost created in the 1940s for the insularity of electric refrigerators and airplanes, in order to replace balsa wood, as it was easier to determine and was more abundant.The froth is created by a colloidal suspension of gas inside a liquid, created by agitation. They are synthesised by the reaction of a polyester polyol with an aromatic isocyanate.

It becomes a froth when little gas bubbles are created utilizing a blowing agent. Prior to the Montreal Protocol, drafted in the 1980s, Chlorofluorocarbons were most normally used as blowing agents. When the froth is still “sticky” , it is formed into a block along a strip of aluminum foil, carried by a conveyer belt, to make the insularity board. As this is a uninterrupted fabrication procedure, the board is cut into set sizes, ready for sale.The boards are comparatively simple to put in. They are cut to the right size to suit within the beams of the roof and are stuck in topographic point with an adhesive.

2.2 In-service Considerations

Expanded polystyrene bead


As antecedently stated, E expanded polystyrene beads are installed into pits, injected through specifically positioned holes ( as stated in the BAA certification ) to guarantee the pit is wholly filled.

A binding agent is assorted with the EPS beads during installing to guarantee the beads remain closely jammed during service.The insularity will non necessitate any farther care, and hence does non incur any farther costs during its service [ 2 ] . As explained in the appendix Figure 1, the life-time of such a merchandise is stated as a lower limit of 125 old ages. The lone excess cost to see is for the stuff and installing of the pit walls.


Expanded polystyrene beads can come in one of two signifiers: as stiff insulating blocks, formed with the usage of a mold under the influence of steam and force per unit area ; or as a loose signifier, ready to be filled into pits. The common signifier of polystyrene beads is in loose signifier, ready to be filled into pits, nevertheless, they can besides be fused into a stiff block signifier under the influence of heat and force per unit area.One of the chief advantages of EPS, EPS is that its belongingss do n’t alter with clip, including fire opposition, compressive strength and thermic conduction ; which is the most of import for the froth in order to function its intent as an insulating stuff. The usage of fire-retarding additives reduces the rate at which fire spreads through the stuff. Alike most other insulating stuffs, the fire opposition of EPS is peculiarly of import in the instance of roof insularity, as there is danger of radiated heat doing roof ignition ( although the brassy ignition temperature of such a stuff is in surplus of 300A°C ) . Due to the location and measure of the stuff, this could do serious harm to the edifice [ 3 ] .As stated in [ 4 ] , “thermal conduction is a step of the rate at which heat is conducted through a peculiar stuff under specified conditions.

” The thermic conduction of EPS depends on the thickness of the filled pit, with a value runing fromhas a value of between 0.035 to 0.04 W/m K.When exposed to moisture, most insularity stuffs will hold a decrease in public presentation and therefore hence affect its on the job life. If there is a high hazard of exposure to wet, EPS would be a good insulating stuff to utilize, as it is H2O impermeable [ 5 ] .The denseness of EPS can change in different classs, but can be every bit small as 15 kg/m3, which remains unchanged during installing into the pit.

Rigid polyurethane froth


The installing of polyurethane is a simple procedure nevertheless it does necessitate cutting down to the right size and determining around the wooden prances of the roof. This procedure takes a comparative sum of clip, but can be achieved merely by utilizing carpenter tools, such as proverbs and files to accomplish the coveted form [ 6 ] .The chief disadvantage with of procedure is that, no affair how skilled the installer, there will ever be some human mistake taking to spreads between the roof construction and polyurethane board. This will ensue in the insularity non being 100 % airtight, and hence losing some of its insulating abilities.Sing this fact, and the ability to do the installing procedure faster and easier, there has been an increased usage of polyurethane spray froth. The froth is sprayed at about 125A°C and 600psi between the roof struts / pits, to a deepness of between 25mm and 40mm.

Bring arounding should typically take less than an hr, go forthing a stiff froth construction that has a similar stiffness and thermic conduction to that of the board signifier [ 7 ] .Alike most other constructing insularity merchandises, the polyurethane froth should last for the life-time of the edifice, if it is remained unaffected by breaks, such as gnawers and WASP droves. Because of this, the insularity should non necessitate any direct care. However, if the loft is converted ( i.e.

into a living infinite ) , the insularity will necessitate to be boarded over.Property: Another popular signifier of roof insularity is polyurethane foamPolyurethane froth is besides a common insulating merchandise, which has a denseness dual that of polystyrene, at 30 kg/m3 ( min ) , which is still considered lightweight, but consequences in a strong board that due to a lower needed thickness and hence, utilizes less infinite [ 8 ] .Despite its comparatively low thickness, the stiff block has an first-class compressive strength of 20-30 KPa. With both closed and open-cell discrepancies available, closed-cell polyurethane is preferred, due to its first-class thermic opposition, compared with other insulating stuffs such as mineral wool [ 9 ] . Figure 1 shows a comparing of some popular insulating stuffs, demoing that polyurethane block requires a dilutant subdivision for an acceptable degree of insularity [ 65 ] ; the thermic conduction is stated as 0.025-0.028 W/m K. [ 4 ]Although non as impermeable to moisture as polystyrene insularity, polyurethane still has first-class H2O defying belongingss with around 8-10 % of H2O soaking up in 24 hours.

2.3 End of Life Issues


Recycling methods for polyurethane froth blocks include:

  • Regrinding the froth into pulverizations so that they can be made into new froths.
  • Adhesive pressure, where the polyurethane granules are coated with a binder which are so cured with heat and force per unit area.
  • Compression molding ; parts are moulded under heat and force per unit area to bring forth stiff 3D parts.
  • Glycolysis produces polyols which are a cardinal natural stuff for polyurethane ; they are made from post-consumer polyurethane bit by responding polyurethanes with glycols at high temperatures.
  • Hydrolysis of polyurethane with H2O green goodss polyols and aminoalkane intermediates. The aminoalkanes can be used as fuels and the intermediates used to bring forth more polyurethane constituents.
  • Pyrolysis breaks the polyurethane down into gas and oil in an O free environment.

  • An advanced signifier of pyrolysis called Hydrogentaion produces pure gasses and oils with the usage of heat, force per unit area and H.

If disposed to a landfill site the polyurethane does non degrade or leach into the dirt.Energy recovery helps to cut down fossil fuel ingestion and new workss have first-class installations for taking atmospheric pollutants once the PU is combusted so hold really low emanations. Polyurethanes can be used as a coal substitutes or a co-fuel when combusted, as it has high energy values. PU stiff froth blocks can populate over 10050 old ages in service and salvage over 100 times the dodo fuels used to bring forth them ; If recycled or put through energy recovery they can salvage even more fossil fuels. The PU stiff froth blocks can easy be removed from edifices at the terminal of their service life as they are merely secured in topographic point.


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Expanded PS beads

Recycling methods for Expanded PS beads:

  • Dissolve the EPS into a dissolver to organize a gel in situ ; , this gel is so treated automatically to make the wanted coveted atom sizes. The mechanical methods include milling, extruders and the formation of pellets.

  • EPS if non in the bead signifier If the EPS is in block signifier, it can be cleaned and processed into beads and thento be used once more.
  • Recycled EPS can be combined with cement and used in foundations ; this adds insulating belongingss ( increases the belongingss ) to better the insulating belongingss of the cement. Up to 80 % EPS can be used and has been in America.
  • EPS can be land and so remoulded into froths, reused and so used in non-foam applications such as stationary or Cadmium instances, or reused in extruder applications

Energy recovery of EPS is much the same as Polyurethanes, new workss have first-class installations for taking atmospheric pollutants so have really low emanations and produce high energy. Discarded EPS does non degrade, so if disposed to a landfill site it will non interrupt down or leach into the dirt.

EPS can easy be removed from service as an dielectric with a big mechanical vacuity ; it can so be recycled or reused in one of the methods above.

2.4 Environmental Issues ( including eco-audit )

An Environmental Audited account or Life Cycle Assessment can be slackly termed as a system for analyzing and measuring the environmental costs associated with a merchandise, activity or procedure.By recognizing and quantifying all energies, wastes and resources which are consumed or released during the full life rhythm of the merchandise we are able to measure the environmental impact of fabricating a merchandise, carry oning an activity or set abouting a procedure.

With this cognition in head it is so possible to quantitatively compare several different alternate attacks to making a merchandise, every bit good as to better incorporate cradle to sculpt design into new coevalss of merchandises.Through the usage of scrutinizing package such as SimaPro or CES it is possible to construct a instance file for both Rigid Polyurethane Insulation boards every bit good as Loose Polystyrene Bead insularity in order to compare the energy outgo at each phase of their life rhythms, every bit good as the C dioxide footmark each green goodss.From the above tabular arraies compiled from the CES stuffs choice package it was so possible to bring forth the undermentioned graphs for both energy and C dioxide ingestion and recovery during each stuff ‘s life rhythm.From these graphs it becomes evident that in footings of both energy consumed and C dioxide produced, polystyrene is the more environmentally friendly stuff ; as in entire ( including terminal of life renewal ) it produces less than a 3rd the sum of C dioxide compared to polyurethane, and expels about half the degree of Energy of polyurethane.Further information on the environmental audit and the full list of factors on which each stuff has been examined can be found in the appendix Figures 2-6.

2.5 Design

Expanded Polystyrene:

  • High quality virgin polymer is used to bring forth the best quality of insularity [ 15 ] , nevertheless the reclaimable nature of polystyrene agencies that beads can be made out of recyclate.
  • Loose-fill beads are by and large combined with a binding agent or adhesive at the clip of injection to better maintain form within loft pit [ 15 ] .
  • Expanded polystyrene bead requires no care one time installed and will last the life-time of the belongings [ 15 ] as it is non biodegradable [ 16 ] .
  • Expanded polystyrene can be melt recycled, downcycled or combusted for energy recovery, taking to easy disposal at the terminal of a edifices life-time [ 16 ] .
  • Use of new fire retardents mean that polystyrene froths now meet fire safety criterions [ 16 ] .
  • Pentane has replaced Chlorofluorocarbons as the blowing agent within polystyrene froths so that they no longer damage the ozone bed [ 16 ] .
  • Loose-fill insularity can conform to any infinite without upseting any constructions or coatings [ 17 ] .

  • The common loose-fill job of “settling” where insularity looses it ‘s opposition to heat flow can be overcome easy by make fulling the infinite to a sufficient denseness proportional to the size of the loft pit [ 17 ] .
  • When compressed into boards a important addition in opposition to heat flow occurs and as a consequence the efficiency of the insularity can frequently duplicate [ 17 ] .
  • The infinites between single polystyrene froth beads may absorb H2O and as a consequence a vapor diffusion retarded may be added to forestall the transmittal of H2O through the insularity [ 17 ] .

Rigid Polyurethane:

  • Large froth blocks can be easy cut down to suit any infinite within a loft and are easy fixed in topographic point through either a covering surface ( such as wood ) being fastened over the top, through the usage of an adhesive or merely through clash between the polyurethane blocks and the environing roof joists.
  • The usage of HFCs or Pentane as a blowing agent mean that polyurethane foam meets current fire safety criterions [ 16 ] .
  • Thermosetting polyurethane can merely be combusted for energy recovery or downcycled [ 16 ]
  • Polyurethane is non biodegradable and as a consequence the froth will last the life-time of the edifice in which it is installed [ 16 ] .
  • The typical usage of low-conductivity HFCs as a blowing agent consequences in a really efficient insulating stuff with a really high degree of thermic opposition [ 17 ] .
  • Polyurethane froth insularity suffers from thermic impetus wherein the low conduction, gasses leach out of the froth to be replaced by air and as such, the thermic electric resistance of the foam beads ; to battle this foil or polymer facings may be added to the froth which can assist brace the thermic electric resistance of the insularity and prevent it from losing efficiency over its lifespan [ 17 ] .
  • Where foil is used as a confronting it may besides move as a radiant barrier which reflects heat back into the edifice and as a consequence increases the overall thermic opposition and so the efficiency of the insularity [ 17 ] .
  • The nature of the high thermic electric resistance values found within polyurethane froth means that a much thinner board can be used where limited infinite is a concern in order to accomplish an acceptable degree of insularity [ 17 ] .

3 Discussion

From our research above it seems that Polystyrene bead is the best pick for the application.

It is easier to bring forth and put in with no farther care costs during its life-time. Polystyrene bead has all the belongingss needed for its application for of roofing insularity, including fire opposition and thermic conduction, all of which are stable throughout its life-time in surplus of 100 old ages. Polystyrene beads have superior H2O impermeableness and have the ability to be made into board which increases its already ample insularity features. When compared with polyurethane which can endure from thermic impetus, whose public presentation can be effected by gnawers and has some installing troubles and disbursals, the polystyrene beads are the superior pick.The effectivity of insularity can be measured utilizing its R-value which is a step of its thermic opposition. In service polystyrene beads can supply a better R-value when higher strengths are needed by increasing the denseness [ 18 ] . At a denseness of merely 2 lbs per three-dimensional pes polystyrene can defy force per unit areas of 10psi [ 9 ] .

However the R-value does non take into history local environmental factors. With respects to the R-Value the polyurethane board comes out the best pick, as it is the most effectual dielectric.Polystyrene is besides highly lasting as its lone ruin is UV visible radiation exposure which is a really rare happening in a loft country.

With edifices operations devouring more than 40 % of planetary resources and continued high degrees of dodo fuel energy usage making pollution and C emanations lending to climate alteration [ 19 ] the environmental consequence of a merchandise is going of all time more of import to consumers. Polystyrene is hence ideal as the energy recovery is a simple procedure with many workss holding the installations for this and as seen in the eco audit table polystyrene is the most eco friendly bring forthing the least C dioxide.

4. Decisions

Polystyrene bead comes out at as the best overall for loft insularity nevertheless each applications individual demands need sing when doing a concluding pick. If the loft country being insulated is a simple rectangular form with a low tallness that could perchance be converted in future so the polyurethane board would possibly be more appropriate. However if the loft is a complicated form and the insularities is traveling to be a more definite lasting fixture so the polystyrene bead is still the most effectual pick. There is besides the consideration that despite the polystyrene being the most environmentally friendly pick the energy salvaging over clip ( ~ 100 old ages ) utilizing polyurethane board could roll up up to really being the more appropriate pick.


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  4. Randall McMullan, “Environmental Science in Building” , Palgrave MacMillan, 2007, p15-17
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  7. Foam insularity, ISo spray roof insulation.Foam insularity. [ Online ] [ Cited: 29 October 2009. ] http: //www.

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