TOPIC: Energy Efficiency
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I am having my roof replaced - and because it is a 12/12 pitch, high off the ground, it is not going to be cheap. I am debating an upgrade to a Dura Tech 5000 finish on 24 gauge metal panels vs going with the standard 26 gauge with what is called an XL finish but putting down an R 4 Low e Thermal Barrier Insulation. Which would benefit me the most in a climate of hot summers but not very cold winters - I have R19 in the roof as house was built in 1976, and lots of skylights to boot. I do not want to spend the extra for the cool roof finish which only comes on the thicker panels, if the thermal layer would help abt as much. I had originally planned on rigid foam panels under the metal but the cost was rediculous.
On an aside, are the cool roof finishes very shiny - is that how they work? I have seen metal roofs that are blindingly shiny as well as matte looking ones and far prefer the matte finish. However, the cool roof finish on these particular panels only offers a matte black which seems an oxymoron. Are cool roof finishes shinier than standard ones?
The coatings that include heat - reflective pigments are not inherently higher gloss than other finishes. As you look at different colors and finishes, you will find a range of glosses and that range is not related to the reflective pigment.
Well, that is good news as I really do not like the glare from the glossy ones I saw. I have requested samples to see - I am hoping for a grey. However, does that mean a finish that calls itself a cool roof in matte black would keep my insulation cooler even tho it is black? I meant to mention, I have clerestory ceilings but we will have roof vents.
In most cases, any color that says it is "cool" should be at least 25% reflective, which meets the Energy Star definition. Generally speaking, the darker the color, the lower the reflectivity. Reflective black is likely 25 - 27%. A reflective tan may be around 40 - 45% and white is around 65%.
We are soon having a black metal roof system installed on our house (I was outnumbered by my wife and 2
daughters on the color choice. I was pushing for a lighter color with a much higher reflective value.)
We live in a very HOT climate in a manufactured home that is not insulated extremely well.
The contractor will be installing the panels over the existing 3 tab shingles. He mounts them to 1x4 battens which are run horizontally.
My question: In your professional opinion, would using a thin perforated aluminum sheeting designed as a radiant barrier placed down on the shingles before installing the battens be worth the $700 cost to purchase enough to cover our roof?
Would this radiant barrier likely result in enough savings over the 30-40 year life of the metal roof to justify the extra cost?
Ultimately, yes, the radiant barrier would have ROI. Something that might have faster ROI though would be to "cross batten". This would entail vertical battens first installed as sleepers along the home's rafters. Then put down the horizontal battens and the roof. The new vertically oriented air chambers then can be vents day bringing fresh air in at the eaves and exhausting it out at the ridge. This will help in getting any gained heat through the roof quickly back outside.
Thank you for taking the time to respond! Your professional insight has been very helpful in making a decision regarding a radiant barrier.
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