More on U-values

I haven't yet started to plot any results, but some early observations appear: Outside, the surface temperatures are always higher than the OAT. The insulated panel is performing best - by far - and the glass is just a tad colder than the solid wood. The glass margin is almost a degree warmer than centre pane, even with Super Spacer. Inside, the glass feels much colder to the touch than either the insulated wood panel and the solid wood rail. This may be a Thermal Capacity issue, but the effect does not change with prolonged touch. The glass always feels colder than the wood. The dawn OAT has been steadily declining for the past week (3 degrees now) so the temperature gradients are becoming significant.

Annoyed with myself today to learn that I had missed the ST advertising deadline for this week. Time then, perhaps, to revise the ad. for the following weekend. It's interesting swinging the changes and watching the changing response in the website analysis. Not enough data yet to make firm conclusions, but enough to consider some changes, perhaps.

Good news, though, on the refurb market front, with a new prospect in view for a big breakthrough. We'll see. On the one hand we have the GREEN agenda: On the other, the economy. Personally, I think the refurb market will benefit, and that brings us full circle, with the windows system designed for just that market in the first place.

The first interesting observation arrived within five minutes of the arrival of the thermometers. With a mild 10 degrees outside and a cool 18 degrees inside, the wood was one degree colder than the inside surface of the glass, but the wood was warmer to the touch. Perhaps I am seeing the difference in thermal capacity. Glass takes heat from the hand more rapidly than from the wood, and the effect of the air in the sealed unit as an insulator is not immediately apparent. I could observe no difference between solid wood and insulated wood panel. With the arctic blast expected tomorrow, and forecast to last for a few days, I should have better numbers to work on.

( PS. I didn't like the small font, so let's try this one)

More on U-values

Infra-red thermometer now ordered, hopefully it will arrive just in time for the coming cold spell forecast for this weekend. A few days of low temperatures outside should give time for temperature gradients to stabilise. Must pop down to Wilco and look for a couple of cheap thermometers to measure inside and outside air temperatures.

The more I think about this, the more I believe I might be on to something. Coated glass may well reflect energy back into the room, but if the internal surface of the glass is colder than the air in the room, (it is) the air in contact with the glass will be cooled by contact, and advect. (Opposite of convect - means cooling by contact with cold surface, and flowing downwards under its own weight. Cold air is heavier than warm, and sinks to the floor, leading to cold feet despite heating set high. It also might properly be described as a katabatic flow - cold air flowing from the hilltops and filling the valleys overnight). Is this loss properly accounted for in the calculation?

Coated glass undoubtedly reduces the energy loss through the glass, but I will still be surprised if more energy is lost directly through the adjacent wood frame which is warmer to touch than the glass.

Franchise enquiries still flowing in. Website analysis shows a growing number of visitors to the site.

More on U values

It's just dawned on me that I already have a 'hot-box': My own home will work perfectly for the purpose. Both front door and back door have almost equal areas of Low-E Superspacer double glazing, insulated wood panels, and solid wood stiles and rails. Daily observations of inside and outside air and surface temperatures should build up a useful database of thermal gradients from which to calculate some correlations (not absolute, but indicative, nevertheless). Not exactly laboratory conditions, but the facility of being able to take multiple frequent observations is a great benefit. I am starting from the assumption that the temperature gradient is directly related to the thermal conductivity of the material or assembly. The steeper the gradient, the lower the conductivity (ie the better the insulation value). This morning, the empirical measurements (the only ones I have until my IR thermometer arrives) tells me that the steepest gradient is in the wood. Am I wrong? We shall see! If I am, then at least I will have a better understanding of the issue if I can see the figures.

RE: Relative thermal properties (November 14, 2008, 06:42:51 PM)

I have a CD with the BFRC prgram on it, but I simply can't be bothered to gather the obscure data needed to fill all the boxes. These estimation programs were supposed to replace the hot box method, which really needs months of painstaking work to build tables from different samples. I suspect your technique would require a grid to sample many points from which your calculation would produce an average. The relative proportion of frame/glass is a hellish complication, which is why I use the BRE calculator. I might suspect its accuracy (I think it's pessimistic) but it does deal with the frame issues.I have found several sites offering hand-held laser/IR gauges for under £30 with claimed accuracy of 2%. Should be good enough for my purposes. I think I will build a box around a redundant doorway in my workshop and use it this winter to run my own experiments. Steady-state temperature measurements with a small lightbulb in the box should produce useful data over a few months. I am only interested in the fundamental (probably gross) difference between a Low E sealed unit and a solid or insulated wood panel using the same glazing method. Should be interesting.

Part of correspondence with Philip Rougier of Fenestration Associates: Follow the whole thing in The windowman forum http://www.double-glazing-web.info/

Progress! The ST ad is bringing in a satisfying number of enquiries to the landing page at www.wvnet.co.uk. in its first week. We already have viable applicant for the Master Fabricator Franchise for Northern Ireland. Early days, of course but heading in the right direction.

I have also started a correspondence with Terry the Windowman's forum about the U-values of timber-framed windows. I find it difficult to believe that wood is a worse insulator than a double glazed unit. My early enquiries appear to show that I might be on to something. I shall dig deeper.

picking up the thread

How did that happen? What happened to September and October?

The Hargould exhibition at Derby was worth a visit for the seminars on 'Green Building'. The commitment of this government to reduce the carbonfootprint of the building industry was made clear, but not how it was to be achieved.
Switching back from pvc to wood wherever possible is likely to become a 'must'. I bet the pvc brigade will do their best to see that it doesn't happen.

I suppose taking a few weeks off saw a good deal of October pass by, and the rest of it was spent with a customer who was one of my first almost 25 years ago. Two failed units and the need for a complete new window in the bathroom gave a good reason to re-glaze the whole front of the house with the latest in Low-E softcoat / Warm-edge units plus new handles to freshen the old windows up and match the new. After all those years, even I was impressed with how easy it went. The Mk I frames came out without too much of a struggle. The glass likewise, after cutting the gunned silicone with a Stanley blade. New sealed units fitted like a glove using the latest SupaKlip locators and knock-in wedge instead of gunned sealant. A fresh coat of Venetian Red to match the new frame in the bathroom, and the front of the house looks like new, at a fraction of the cost of all-new windows.

Onwards and upwards. The next item out of the workshop will be a mix of casement and rising sashes in SupaWOOD, painted white. I can't wait!

The "greening of England" 4

Apart from its ‘natural’ origin, timber as a construction material differs in one fundamental way from both plastic and aluminium: That is, of course, the finishing process.

Aluminium is anodised before it is cut into components and assembled into frames, whilst pvc comes out of the extruder as a finished product.

Much of the focus of the production process for the latter materials is in preventing damage to the finish, as repair is always difficult and expensive, requiring that elusive skilled labour again.

Timber, on the other hand, is traditionally worked in the raw, and the final finish is applied to assembled frames, sometimes after the hardware is fitted. Most unsatisfactory.

To complicate matters, there has been a sea-change in the way wood-finishes themselves work. Although micro-porous finishes have been around for more than forty years, until about twenty years ago traditional oil-bound paints were still predominant and in common use. These were impermeable, sealing the timber and to a great extent limiting the seasonal movement of moisture in and out of the timber. They were usually applied on-site by a decorator who might or might not remove the hardware first.

The main drawback was their tendency to split and flake, letting water in. That couldn’t get out, and once in, it encouraged fungal growth in the wood under the paint, which blew more of it off. When micro-porous translucent finishes became common during the 1980s, they stopped all that, and transformed the maintenance requirement. The downside was that seasonal moisture changes led to massive dimension changes, too. The designs had to accommodate this. No problem with modern styling, but more difficult to retain a true traditional appearance.

The next big change was from solvent-borne finishes to water-borne, for Health and Safely reasons. Like all things in life, there were advantages and disadvantages.

The one big advantage of water-borne finishes is the short drying time. Minutes or hours instead of days (especially in the winter). Another is the thick film-build possible in each coat. The downside is the relatively poor stain penetration, so the underlying colour of the wood influences the final finish. This can vary from piece to piece, or even from place-to-place in some timbers. Water based finishes don't "wet" the surface of the wood as well as white spirit, and can leave the open-grain hardwoods with a fine pitted appearance. In reality, they are fine air-bubbles that need heavily overcoating to close.

Although the technology is improving all the time, it is true to say that the first five years of the change-over period of the mid-90s were a continuous nightmare. Frames sticking to each other, even a week after they were sprayed: Little runs and sags that simply could not be touched-up, but needed stripping and refinishing: Blotchy, uneven colours, and much, much, more.

I am very pleased to report that these problems are now a thing of the past, but, believe me, it made staying with wood windows difficult at times.

Recent developments make it all worth while…..

More next week.

The 'Greening' of England (3)

Why SupaWOOD?

The SupaWOOD system was designed to be a complete departure from traditional joinery in all but appearance. Trade skills have been declining for decades. In a technological age, hand/eye skills have not been fully appreciated, and the failure to allow schools to teach vocational skills have meant that the traditional apprenticeship all but died in the latter half of the 20th Century. The cost of running a traditional joinery shop just rose, and rose again as the prevalence of good tradesmen steadily declined. I decided that the way forward was to design a framing system that treated wood as just another engineering material. Fully finished components should be assembled by fitters in much same way that a motor car production line works.
No glue, no careful trimming and fitting. Just screw and snap accurately made and finished parts together. The manufacturing process relies on Production Engineers rather than joiners. Once the tooling and machinery is set up, repetitive production is simple in comparison with the traditional model.

The pre-finished, pre-glazed cassette system de-skills the installation process, and sets wood windows on a par with pvc. Fitters of the SupaWOOD window need no woodworking skills, just as fitters of pvc windows need no plastic working skills.

That’s it.

The whole range started with one small window and ended up as a complete range of interconnecting frames to form bows, bays, and conservatories, with inward and outward opening residential doors, french doors and sidelights, inline sliders, rising sashes, in almost any combination you care to use. They all share one characteristic: The 20mm sealed units are dry channel glazed into ex 2” (50mm) profile to preserve a traditional appearance suited to the vernacular architecture of the British Isles.

For more than twelve years, the inline sliding patio doors were supplied to a competitor in flat-pack form – two doors, three doors, four doors, overdoor lights, almost any combination in standard sizes and made-to-measure. I am particular proud of the low (all but zero) call-back rate. Those few call-backs out of thousands of units were mostly due to failures in the assembly or adjustment process, although until a proper piece-rate bonus system was set up in the factory, I confess we did manage to sent out incomplete kits from time to time. A system of rewards and penalties for the workforce soon stopped that.

Sliding patio doors fell out of favour during the 1990s, to be replaced by a love affair with french doors, which continues today.

More next week.

The "greening" of England (2)

A big problem with traditional wood windows is that they do not take sealed unit double glazing well. Even when heavily modified to accept sealed units, the edge cover or the drainage (or both) is often inadequate, or the frame is excessively bulky. That doesn’t stop manufacturers making them and customers buying them. By the time the problems show up, the seller is often long gone. I have stood in the lounge of the very expensive home of a retired Captain of Industry who was apoplectic with rage because he couldn’t see out of a single one of his large picture windows. All of them fogged up just one year past their 5-year guarantee, and the manufacturer (not me) had shrugged his shoulders and walked away.

The problems first became evident to me many years ago when I was asked to replace a neighbour’s 1930s bay windows. I made them out of untreated softwood, primed the frame, then bedded 14mm sealed units in butyl mastic (I said it was a long time ago) leaving the customer to paint the topcoats himself. Not ideal, I decided.

A year earlier, I had been building loft conversions as a sub-contractor, and had discovered that an aluminium window went in, fully finished, in about two hours, but next day the customer was bending my ear about the gallons of water all over the floor (from condensation, of course). (PVC hadn’t yet arrived in the UK, although there were rumours of them appearing on the continent).

A wood window, however, (usually a stock item from the Boulton and Paul catalogue) glazed with stepped units looked horrible and took days to install, glaze and paint. Out on a 45 degree roof, in the rain or snow it was no fun at all, and I soon decided there must be a better way to make a wood window.

After the experience with the softwood bay, I sat down with a sharp pencil and a clean sheet of paper and designed the first prototype of the Supawood window.

I decided from the start it had to be:
· a good-looking product that would sell to my customers in traditional Warwickshire cottages
· technically excellent
· fully finished in the factory before glazing.
· glazed in the factory before installation
· capable of being installed in a flash in all weathers.
· Guaranteed zero-callback (ie no jamming, warping, or swelling to deal with)

From the start I concluded that channel glazing was necessary to get a 20mm sealed unit into a traditional 2” profile, and mechanical fixing was necessary to allow the glazing to be replaced if necessary. The early versions still involved carrying heavy glazed sub-frames up ladders, but that was soon changed in favour of an inside fitting version, and it fast became clear that there was no way I would ever want to return to carrying glass up a ladder in the rain.

The development of the present version took many years of continuous refinement, with some useful ideas coming up along the way. It’s a long story with many twists and turns, but it does look as if, with the advent of this new miracle timber, the SupaWOOD window is about to truly justify its name.

More next week.

The "Greening" of England

Anyone who truly believes in making the world a greener place will welcome the latest brilliant development in timber technology.

Just imagine a miraculous discovery of the 21st Century:

A timber that :
· Is more durable than teak.
· is a plantation crop with a growth cycle of just 35 years
· can be recycled, burned, buried, or otherwise disposed of with no nasty consequences

better still...
· machines better than any hardwood
· takes a better finish than pine, as durable as pvc
· has no knots and comes in 6m lengths to minimise wastage.



A material such as this would be truly miraculous, and who could doubt its advantage in “green” terms over any plastic or metal: Just plant a seed and stand back for 35 years.
The small amount of energy required to fell, transport, convert, and machine it into useful products would pale into insignificance compared with the energy required to extract, smelt and refine aluminium, or to produce the chemicals from which pvc is manufactured.

Well, believe it or not, that material is here.
This wonder material of the 21st century actually exists.

And guess what: The ancient Romans understood the basic process, even if the technology to make it work in economic terms had to wait almost 2000 years.

The fundamentals are simple:
Soak any timber in vinegar to improve its rot resistance.

A more sophisticated process to impregnate softwood with commercial acetic acid was first proposed in 1928, and the race has been on since then to develop a commercially viable process. Only in recent years have the Dutch succeeded in bringing a commercially viable product to the market. They have branded it as a new species, and it certainly behaves like no timber I have ever previously encountered in a woodworking career spanning more than 35 years.

Because extensive trials with these acetylised timbers have been carried out over many decades, there is a massive database to back up the claims. The Building Research Establishment (BRE) for example, will back a 60 years lifetime, even in the most demanding wet and heavy applications. Treated timber used for canal lining has, after ten years in service, not shown the slightest deterioration.

Of almost as much interest to this joinery designer is the fact that it just does not absorb water at all. After extensive soaking of test-pieces, the swelling I have measured is less than 0.5% (yes, that’s less than half of one percent) compared to the usual expectation of between 5% and 8%.

That means the annual winter swelling/summer shrinkage of windows and doors can be consigned to the past.

Having beaten my head against the brick-wall of consumer resistance for more than two decades (we prefer zero maintenance upvc, dear), the answer is here:

SUPAWOOD WINDOWS DOORS AND CONSERVATORIES MADE FROM THIS WONDER MATERIAL OF THE 21ST CENTURY ARE EVERY BIT AS DURABLE AS PVC, AND INFINITELY LESS POISONOUS TO OUR PLANET

More next week.