Comments on: This Playground Slide Can Give You a Feel for Building Science

By: Jim

Jim — Wed, 01 Aug 2012 18:13:03 +0000

Railroad is still going
Railroad is still going strong at Hermann Park. http://www.hermannpark.org/railroad.php . Lots of other cool stuff there now.

By: David Butler

David Butler — Mon, 30 Jul 2012 22:07:53 +0000

MJ wrote:

MJ wrote:
> Living in Texas I figured those things were pretty scarce.

I'm sure that's true.

> Would such a retrofit really be more expensive than getting the ducts and ceiling plane sealed?

I don't know what the spray-on stuff costs, but I'll eat my shoe if it's a better value. Also, I recall a report that indicated the performance is much worse than you suggest.

> Building Science people like to talk about the ideal

I'll admit my focus is new builds, but ideal? I don't think so. I'm all about finding value, not perfection.

By: M.Johnson

M.Johnson — Mon, 30 Jul 2012 15:40:04 +0000
Okay, it appears I glossed
Okay, it appears I glossed over the term "... in tight, well-insulated new homes" when referring to the effectiveness of radiant barrier. Living in Texas I figured those things were pretty scarce. I would really like to get a clear picture on what proportion of new and old homes can be described as such.

I understand spray-on RB is the labor saving choice for retrofits, about 75-80% as effective as the foil type (in addition to covering rafters too). Would such a retrofit really be more expensive than getting the ducts and ceiling plane sealed? I have had difficulty even getting a reasonable quote for the latter.

I understand Building Science people like to talk about the ideal, about new construction with good air sealing everywhere and maybe even ductwork in enclosed space. My concern is, 99% of us live in something very different and studies focusing on retrofits is so very valuable.

By: David Butler

David Butler — Mon, 30 Jul 2012 11:14:40 +0000
@MJ: in addition to Blasnik's
@MJ: in addition to Blasnik's presentation, I believe the FSEC study you mentioned was based on retrofit in not-so-great homes (maybe MB's citation was based on that study).

The thing is, retrofitting a radiant barrier is seriously expensive laborwise. Can't imagine it would be the best use of client's money if attic plane or ducts haven't first been sealed. But once you've take care of that...

Do the numbers and you'll see it just doesn't pencil out, except perhaps for DIY'ers. I'd like to know what you'd need to charge to install a RB in my attic.

In new construction, a radiant barrier adds less than 10 cents per ft2 when factory applied to the roof sheathing. That might have a decent payback in a hot climate like Houston.

By: Paul Raymer

Paul Raymer — Sat, 28 Jul 2012 18:03:39 +0000
Allison, I pondered this for
Allison, I pondered this for awhile and came to the conclusion that the reference to building science was that it has its ups and downs. You climb to the top and the next thing you know ... swittpt blam! By the way, the slides in Central Park were all metal and there was nothing soft to land on at the bottom. Asphalt, baby! NYC people are tough.

By: Michael Blasnik

Michael Blasnik — Sat, 28 Jul 2012 17:46:16 +0000
M. Johnson -- Actually, there
M. Johnson -- Actually, there is no contradiction. The Houston study was of Energy Star homes which had tight and well insulated ducts and good ceiling insulation and so the savings potential for radiant barriers was much lower. The other presentation you cite was based on estimated retrofit savings for existing homes with not very tight or well insulated ducts or ceiling.

Asking for a single number for radiant barrier savings is like asking what adding R-19 to your attic will save. The answer very much depends on the existing conditions. If you start with R-38 then you wouldn't save much compared to if you started with no insulation.

By: Rob George

Rob George — Sat, 28 Jul 2012 00:08:56 +0000
I just can't pass this up!
I just can't pass this up! Our playground slides were in Minnesota where they didn't get very hot. We solved the friction problem by saving the waxed paper from our lunch sandwiches to wax the slide! I don't think today's plastic bags would do the same. And didn't you just love the merry-go-rounds?

By: Chris Brown

Chris Brown — Fri, 27 Jul 2012 20:43:42 +0000
OK Allison, you have to admit
OK Allison, you have to admit it, while the slides in Hermann Park were cool (or hot as you describe), the mini-train was way cooler! Wound all the way around the duck pond. Every time we went to the zoo required a ride on the mini train. Remember

the "engineer" with the official engineers cap? Probably a thing of

the past now. Haven't been to the Hermann Park area in decades. Thanks for jogging a summer memory!

By: David Eakin

David Eakin — Fri, 27 Jul 2012 18:51:56 +0000

I listened to a Webinar a
I listened to a Webinar a couple months ago where a proponent of radiant barriers was describing their product’s operation. He described how the heat radiated downward from the roof would be reflected by the material into the 3/4″ space between the roof deck and the reflecting material – but there was no test data as to what that space’s temperature would be – just that the heat would be “dissipated”. I think I could see (intuitively) how a 2-roof system – with reflective barrier on the top of the inner roof – might work as it would be reflecting solar heat gain into the ventilation space between the 2 roofs instead of the attic, but I’d also like to see some experimental research data on it. I suspect that the end result will be that you cannot beat reflective roofing surfaces for solar gain reduction.

By: John Poole

John Poole — Fri, 27 Jul 2012 17:44:41 +0000
Funny, at the same time you
Funny, at the same time you were sliding in Houston, I was sliding down a similar metal slide in this little playground somewhere near a corner of Victory Drive in Savannah, GA, where my mom would take me when we were visiting my great aunt. Same situation: Very hot sunny area; fun until you came in contact with the metal.

BTW, you can also reduce friction by laying flat on your back, if you don't mind bonking the back of your head on the seams (I re-discovered this as an adult on a water slide some years back, where I stupidly sat up and couldn't figure out why I wasn't sliding!)