Kitchen garden bay window heatloss problem?

D107

the Ventana 2050 garden window. 60H by 42W, Low-E glass and R5 insulation under the seatboard. Has an overall R-50 rating.

http://ventana-usa.com/windows/series_2050_garden.html

I think it would add alot of class to the kitchen; the marble counterop would extend right into it. Glass shelves for hanging plants. Wife has been waiting for a new kitchen for a LONG time; initially didn't want the window but then she saw one installed.

My concern is infiltration in and heat loss in general with that much glass. As it is we'll be reducing our radiator size tremendously due to severe space requirements. We probably won't be able to deal with something really fancy like radiant heat around the window frame. In house overall, CI heat load is 3 to heat loss 1, so with living room opening up to living room and dining room we expect some extra coverage from those rads. Window faces northeast.

Bottom line, even if the room overall is kept warm, we don't want anyone working at the counter/sink area to be feeling cold. (Especially with those cold granite countertops.) I won't put any electric elements in.

Just wondering if any of you have had any experience with this.

Thanks,

David

jp_2

R50???

what the heck does that mean?

can't see how that could mean R-value of 50?

i'm puzzled?

R5 between granite counter and the great outside? I'd say asking for unhappy dishwashers.

D107

thanks--says 'AAMA Certified R-50 rating'

I don't know 'AAMA'--I assume it was an insulation rating. 'the only vinyl garden window on the market today' with that rating. Just spoke to the company. They say the R-50 rating is for the entire window (vinyl and glass together). They also have a DP-50 Design pressure rating for impact (earthquakes, etc.)

If a 1-inch thick R-5 piece of insulation board is placed under the seat board, R-value from bottom is increased to R6.22. I gather that's not against the outdoors, but from the bottom. But since the window juts outside, I'm confused, unless that board only insulates where it touches against the solid bottom before it juts outside.

On the one installed window I inspected, there didn't seem to be a problem, but I was there briefly and there may have been sun shining in. Our window gets very little sun, almost none in winter.

Make any sense?

Thanks,

David

GMcD

Be wary

Here's a link regarding the AAMA (American Architecural Manufacturers Association) attempt to have their "alternate" window rating "standard" integrated into fenestration rating standards that are currently based on the NFRC (National Fenestration Research Council)standards:

http://news.glassmagazine.net/issues/2007-06-05/email.html

I looked though the website on those Series 2050 bay windows and there is no data on what kind of glass they are using or what the "R-50" actually means. As far as I know, the highest performing insulating glass out there is the Heat Mirror Super triple film unit that can provide a near R-20 thermal performance (centre of glass), with krypton gas fill. Link: http://www.businesswire.com/portal/site/google/index.jsp?ndmViewId=news_view&newsId=20071207005042&newsLang=en

So, to get an "overall R-50 Thermal heat transfer performance", the framing would have to near infinity for thermal reistance to make up for the area of R-2 glass, to get a combined overall "R-50" thermal rating.

I smell oil of slithering creatures.

Roland_9

Rating Confusion

Could it be a typo? Could it actually be a "DP-50" rating? If so, it stands for 'Design Pressure' or how the window can withstand rain and wind pressure. I'm looking to install such a window (different brand) in my own home and didn't think to inquire about this rating until this topic came up.

D107

thanks Geoff for your due diligence

It does seem a bit strange to say the least.

Bottom line is: with my house walls having 4" of blown in cellulose plus 3/4" styrofoam over the old wood clapboards under the vinyl, the walls themselves, adding the plaster, lathing, 3/4" sheathing, probably don't provide more than an R-15. My current 20 yr old thermal windows are probably no more than R4 according to the manufacturer and they certainly conduct quite a bit of cold into the house, though I'm sure they're better than the old wooden ones they replaced.

Can't log on now for some reason to the NFRC site to see if this product is listed there...

But if the whole thing was only an R10 let's say, might that not be good enough or is the design, size and amount of glass (and of course possibly suspect ratings) an invitation to problems?

Thanks,

David

PS to question by Roland: doesn't seem to be a typo. Though on the phone they first anwered my query on R-50 with an explanation of DP-50; then when pressed about the R50 she conferred with superiors and came back with 'R-50 rating is for whole window. Go figure.

Nikolasvipam

DP Ratings on Windows

Design Pressure (DP) – A design pressure rating, as created by the American Architectural Manufacturers Association (AAMA)/Window and Door Manufacturers Association (WDMA) 101/I.S.2-97, is a measure of the amount of pressure a window or door is designed to withstand when closed and locked. Each DP rating also establishes other performance factors such as structural pressure, water penetration and air infiltration. The higher a DP number a window or door has, the better the performance. As a frame of reference: DP 40 means that a window or door is tested to 60 pounds per square foot equal to a 155 m.p.h. (250 km/hr) wind and must withstand water penetration under conditions equal to 8 inches (20cm) of rain per hour driven by 50 m.p.h. (80 km/hr) winds.
Two things to remember, is the window a casement or dlb hung. Most casements (wood or Woodclad) start at 35 then go to 50 and 65 DP ratings. What usually chances the spec on casements is the glass thickness. Thicker glass higher rating, and effect wind load. Now Dlb hungs are much different, besides glass there can be clips at the checkraid for Structural and higher interior bottom stop for to prevent water. Hope this helps.

mike parnell

garden window

I got a garden window 6-0x3-0 above my master jacuzzi with ceramic tiles into it ,like your marble. I put 2"more ridgid insulation under it , it faces direct north , im happy with it, you could put some radiant under your counter tops. good luck.....mike

Steamhead (in transit)

Here's a red flag

"we'll be reducing our radiator size tremendously due to severe space requirements"

Who says you HAVE to do that?

I wouldn't trust this "designer"- such people don't have to actually use the cold kitchens they inflict on people. Find someone else.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

D107

Thanks Frank, well we've already decided against the

window, but the current ci rad is about 4X the heat loss, and hidden behind an island, so we're probably not getting all those BTUs anyway. We figure with a small CI rad or a Governale Gov-Ray we can probably match and then some the room heat loss of 1500btu and it will probably circulate heat better in its new location. Heat loss should be less too with a big increase in amount of cabinets.

I agree, though, kitchen people generally know little about heating. Many well-meaning designers seem hooked on a group-aesthetic (keeping up with the Joneses) where countertops must be granite, windows garden bay, appliances commercial Viking. Great if you've got 100K for a kitchen.

There will be a time when we'll have to temporarily run a bypass in order to remove the kitchen rad link in the series chain of rads, and we should get some idea of the heat requirements.

Thanks,

David