Sofa shopping

17 04 2015

We did a series of posts on how to evaluate a quality sofa about two years ago, and judging from the questions we get from people, we thought it might be time to re-post these!  The 3-part series is divided into evaluating a sofa frame, cushioning materials and fabric (of course!).  Herewith, the first post:

So you’re shopping for a sofa, and you see this one in a store.

camille 1

In a different store, you see the one below.

blue sofa

One sofa (the one on top) costs $3000;  the other costs $1500.  Why the wide disparity in price?

Shopping for a sofa is fraught with anxiety – we don’t do it often (for most people it’s every 7 – 10 years) so we don’t know how to shop for it.  Knowing what to look for, and how to evaluate a sofa, might take some of the anxiety away.  And knowing a bit about the components and how they’re put together will explain some of the difference in price.  It’s important to keep that in mind while you’re being seduced by the alluring upholstery, svelte arms and come-hither cushions.  But if your darling’s joints are weak, springs loose and cushions flat, you’ll quickly lose that lovin’ feeling.  Not to mention the additional chemical guests you’ll be inviting into your home with the sofa.

Start by asking yourself questions such as who will use the sofa  – will the kids dump themselves and their bags on it right after school or is it in a room that’s just used for entertaining?  How long do you want it to last?  Do you want to sink into the cushions or sit up straight?  Nap on the sofa?

One of the first things you should do – really before doing anything else –  is look at the sticker price and concentrate on the amortized cost  (cost per day) of buying each one.  There is a reason for the price disparity – they have to cut corners someplace, so lower quality materials are used

And construction is …  well let’s just say it’s not built to last.  “Quality” translates into “useful life”.  For simplicity, let’s assume the top sofa will last 20 years while the bottom sofa will last just 5.  That would mean the top sofa costs $0.41/day while the bottom sofa costs $0.82/day = exactly double.  The cost of owning the top sofa is half as much as the cost of owning the bottom sofa.

Dr. Thomas J. Stanley, in his book The Millionaire Mind, observed: “By definition, millionaires tend to be accumulators, a trait they inherited from their parents who were collectors.  Their parents and grandparents held on to things that had value. So the majority of millionaires have a family legacy of collecting, saving, and preserving.  Waste not, want not is a theme acted out by first-generation millionaires today”.[1]

With regard to how this trait applies to buying furniture: They deliberately purchase furniture they can pass on to the younger generation.  This, in essence, is their definition of quality furniture.  It will outlive a person’s normal adult life span, will never lose its appeal, and will probably appreciate in value.[2] A good quality sofa is an investment, like any other quality purchase that you expect to last.

For the next few weeks I’ll break a sofa down into component parts and talk about each one separately, starting this week with the frame and suspension system:

FRAME:

A very low cost sofa is probably made of engineered wood – such as plywood, particleboard, Medium Density Fiberboard (MDF) or glulam  –  all of which can legally be referred to as “solid wood products”.   Engineered wood (or composite, man-made or manufactured wood) are made by binding the strands, particles, fibers or veneers of wood with adhesives – most often that means urea formaldehyde (a known carcinogen) and finished with polyurethane or aluminum oxide.  In laymans terms, MDF (for example) is sawdust held together with glue.  MDF has a life span of 1/10th to 1/4th that of solid wood, properly constructed – and costs about 1/10th to 1/4th that of solid wood.  Cutting, sanding, or releasing particles of MDF into the air might be a high risk and should be avoided.  If the MDF isn’t properly sealed, it can leak formaldehyde for years, pumping it into your home or office.

Often manufacturers use wood veneers over MDF cores, and consumers have no idea that they’re not buying real wood.  Veneers are also used on solid wood (usually a less expensive wood) –that has a similar property as the veneer, allowing them to swell and contract together with changes in humidity.  They also respond similarly to stain and finish products. The bond between manufactured wood (MDF) and the veneer is not as strong or stable as that of the solid wood because MDF tends to respond more dramatically to changes in humidity and temperature, and is more rigid than solid wood, making the bond less durable.

Recognizing solid wood veneer furniture is fairly simple. Look to the bottom and back edges of tabletops, drawers and shelves. Solid wood always has grain, whereas MDF and particleboard do not. These unexposed edges will not typically be veneered.

Another thing which is often cited as a way to evaluate quality is to pick up the sofa – if it’s really heavy, it’s probably made of solid wood – or so the saying goes.  However MDF is also very heavy – so weight alone cannot really be used as a test.

At the next step up, soft woods (like pine) may be used.  The highest quality furniture uses kiln dried hard wood, like ash, maple or poplar, which offer greater strength and stability.  But not all wood is created equal: we think that it’s important to choose a wood that did not come from an endangered forest (such as a tropical forest), and preferably one that is sustainably managed, because forests, according to the National Resources Defense Council, are critical to maintaining life on Earth.  And that’s something we should pay attention to!   (See our post about wood used in furniture at https://oecotextiles.wordpress.com/2012/08/23/how-to-buy-a-quality-sofa-part-2-wood/ )  Wood certified by the Forest Stewardship Council (FSC) ensures that the wood used in your sofa was from a managed forest. SFI, an alternative certification created by the American Forest & Paper Association, allows such things as clearcuts, use of toxic chemicals, and conversion of old-growth forests to tree plantations. So the certifying body matters!

How the wood is connected is important too.  Lower cost sofas are often stapled together, or you’ll get plastic legs screwed into the frame instead of wooden legs that are part of the posts or bolted into the frame.   Give it a year or two and the arms get loose or the frame wobbles.  Higher cost sofas are held together with glue and dowels or tongue-and-groove joints, making the joints even stronger than the wood itself.  Corner blocks (in each corner of the frame, near the legs, an extra piece of wood joins the two side rails) are important.

Finally, the wood is often stained or varnished – both of which emit harmful VOC’s of various kinds, depending on the stains or varnishes used.  A safe alternative is to ensure that the stains/varnishes used don’t emit harmful VOC’s such as formaldehyde, and are formulated without aromatic solvents, heavy metals in the pigments, toluene solvents or other harmful chemicals.

SUSPENSION SYSTEM:

The suspension system determines the bounce in the cushions, and how they support your weight when you sit on them.   The differing degrees of pressure your body puts on the cushions causes the coils to respond, giving what is known as “ride”.  Generally, the higher the number of coils, the better the ride.  The gold standard has always been the labor-intensive, 8-way hand-tied spring system. It’s expensive to do it right, and few companies do. When done correctly each spring is set into the deck webbing and attached, with various spring rates depending on what portion of the seat deck its located. They are then tied together (8 strings per piece) and knotted at each juncture (not looped! – only knotting keeps the spring deck together if a string breaks). Much has been said about how eight-way hand-tied spring-up systems are superior to any other kind. “It’s a sacred cow in the industry,” says Professor C. Thomas Culbreth, director of the furniture manufacturing and management center at North Carolina State University [3].

But not all eight-way hand-tied spring-ups are built the same way, and the sinuous spring – or S –  system,  will last just as long, and for most people the comfort level is the same.  Sinuous springs are “S” shaped and run from the front of the seat to the back. These springs are supported by additional wires that cross from side to side.  The S springs lack the localized response of a coil system but gives a firm ride that some people prefer, and it has less potential for sagging over time.   It also makes for a strong seat, and it might be the preferred option in a sleeker style as it requires less space.

Next week we’ll tackle cushions, because that’s, as they say, a whole ‘nother ballgame.

[1] Stanley, Thomas J., The Millionaire Mind, Andrews McMeel Publishing, 2001, p.294

[2] Ibid.

[3] http://money.cnn.com/magazines/moneymag/moneymag_archive/2003/03/01/337933/

 

 





Embodied energy needed to make one sofa

6 01 2010

I just read the article by Team Treehugger on Planet Green on what to look for if you’re interested in green furniture. And sure enough, they talked about the wood (certified sustainable – but without any  explanation about why Forest Stewardship Council (FSC) certified wood should be a conscientious consumers only choice), reclaimed materials, design for disassembly, something they call “low toxicity furniture”, buying vintage…the usual suspects.  Not once did they mention your fabric choice.

Of course, all these are important considerations and like most green choices, there are tradeoffs and degrees of green.  But if we look at the carbon footprint of an average upholstered sofa and see what kind of energy requirements are needed to produce that sofa, we can show you how your fabric choice is the most important choice you can make in terms of embodied energy.  Later on (next week’s post) we’ll take a look at what your choices mean in terms of toxicity and environmental degredation.

These are the components of a typical sofa:

  • Wood
  • Foam (most commonly) or other cushion filling
  • Fabric
  • Miscellaneous:
    • Glue
    • Varnish/paint
    • Metal springs
    • Thread
    • Jute webbing
    • Twine
  1. WOOD: A 6 foot sofa uses about 32 board feet of lumber (1) .  For kiln dried maple, the embodied energy for 32 board feet is 278 MJ.  But if we’re looking at a less expensive sofa which uses glulam (a laminated lumber product), the embodied energy goes up to 403 MJ.
  2. FOAM:  Assume 12 cubic feet of foam is used, with a density of 4 lbs. per cubic foot (this is considered a good weight for foam);  the total weight of the foam used is 48 lbs. The new buzz word for companies making upholstered furniture is “soy based foam” (an oxymoron which we’ll expose in next week’s post), which is touted to be “green” because (among other things)  it uses less energy to produce.  Based on Cargill Dow’s own web site for the BiOH polyol which is the basis for this new product, soy based foam uses up to 60% less energy than does conventional polyurethane foams.   Companies which advertise foam made with 20% soy based polyols  use 1888 MJ of energy to create 12 cubic feet of foam, versus 2027 MJ if conventional polyurethane was used.  For our purposes of comparison, we’ll use the lower energy amount of 1888 MJ and give the manufacturers the benefit of the doubt.
  3. FABRIC:  Did you know that the decorative fabric you choose to upholster your couch is not the only fabric used in the construction?  Here’s the breakdown for fabric needed for one sofa:
    1. 25 yards of decorative fabric
    2. 20 yards of lining fabric
    3. 15 yards of burlap
    4. 10 yards of muslin

TOTAL amount of fabric needed for one sofa:  70 yards!

Using data from various sources (see footnotes below), the amount of energy needed to produce the fabric varies between 291 MJ (if all components were made of hemp, which has the lowest embodied energy) and 7598 MJ (if all components were made of  nylon, which has the highest embodied energy requirements).  If we choose the most commonly used fibers for each fabric component, the total energy used is 2712 MJ:

fiber Embodied energy in MJ
25 yards decorative fabric/ 22 oz lin. yd = 34.0 lbs polyester 1953
20 yards lining fabric / 15 oz linear yard = 19 lbs cotton 469
15 yards burlap / 10 oz linear yard = 9.4 lbs hemp 41
10 yards muslin / 7 oz linear yard = 4.4 lbs polyester 249
TOTAL: 2712

I could not find any LCA studies which included the various items under “Miscellaneous” so for this example we are discounting that category.  It might very well impact results, so if anyone knows of a study which addresses these items please let us know!

So  we’re looking at three components (wood, foam and fabric), only two of which most people seem to think are important in terms of upholstered furniture manufacture.  But if we put the results in a table, it’s suddenly very clear that fabric is the most important consideration – at least in terms of embodied energy:

Embodied energy in MJ
WOOD: 32 board feet, kiln dried maple 278
FOAM: 12 cubic feet, 20% bio-based polyol 1888
SUBTOTAL wood and foam: 2166
FABRIC: FIBER:
25 yards uphl  fabric/ 22 oz lin. yd = 34.0 lbs polyester 1953
20 yards lining fabric / 15 oz linear yard = 19 lbs cotton 469
15 yards burlap / 10 oz linear yard = 9.4 lbs hemp 41
10 yards muslin / 7 oz linear yard = 4.4 lbs polyester 249
SUBTOTAL, fabric: 2712

If we were to use the most egregious fabric choices (nylon), the subtotal  for the energy used to create just the fabric would be 7598 MJ – more than three times the energy needed to produce the wood and foam!  This is just another instance where  fabric, a forgotten component,  makes a profound impact.

(1)  From: “Life Cycle Analysis of Wood Products: Cradle to Gate LCIof residential wood building material”, Wood and Fiber Science, 37 Corrim Special Issue, 2005, pp. 18 – 29.

(2)  Data for embodied energy in fabrics:

“Ecological Footprint and Water Analysis of Cotton, Hemp and Polyester”, Stockholm Environment Institute, 2005

Composites Design and Manufacture, School of Engineering, University of Plymouth UK, 2008, http://www.tech.plym.ac.uk/sme/mats324/mats324A9%20NFETE.htm

Study: “LCA: New Zealand Merino Wool Total Energy Use”, Barber and Pellow.