I've lived in both North Carolina and Minnesota. I installed a radiant barrier in North Carolina and was very impressed by the results. Now in Minnesota there are only about two months that are hot enough to warrant it. Does radiant barrier help in any way in the winter?

Views: 2070

Reply to This

Replies to This Discussion

I doubt you would see much benefit from a barrier in MN. From my research only the far southern states get much benefit but even then they need to focus on air sealing and having high levels of insulation.

 

The priorities in a home should be air sealing the attic floor and then insulation. Since you have to get under the insulation to air seal the air sealing has to come first.

 

You also need to understand insulation and radiant heat. Insulation is not a radiant barrier, a barrier reflects radiant heat, but insulation will stop radiant heat at the right depth. Fiberglass is a very open insulation with lots of air spaces and radiant heat will travel deeper into the insulation. With foams and cellulose the radiant heat is captured closer to the top of the insulation giving better protection from the heat.

 

ORNL had a savings calculator for radiant barriers on their website. If you played with it you saw that under insulated homes gained the most benefit from a barrier. As the level of insulation was increased the benefit decreased. So the more insulation you had the less benefit you received the from barrier and the less cost effective it became. With a well insulated home there was a 1-2% savings on AC, not the entire heating AND cooling costs.

 

In my area a couple of companies are selling the barrier at $1 to $1.50 a square foot laid out on the attic floor.  ORNL says that dust degrades the effectiveness of the barrier in 1 to 10 years when laid on the Attic floor. Where as dust will have no effect on air sealing and insulation.

 

You should also learn about differences in insulation and how they perform in different installations. As we know fiberglass is very air porous and does not perform close to its full potential when there are air currents washing over it. Its like stepping outside on a cold windy day and feeling the air blow right through that sweater that was keeping you warm in the house. A wind breaker over it does a lot to keep you warmer on the windy day. Cellulose does a much better job of trapping and holding the air when left uncovered and performs better in the attic. The settling that occurs actually helps trap the heat and is not a bad thing. Cellulose over the top of fiberglass is almost like a windbreaker over a sweater.

 

If you heating degree days are close to or exceed you cooling degree days then you are better off spending you money on other energy saving projects. Since barriers lose their effectiveness due to dust when laid in the attic floor I do not think that is a worth wile way to install it in any location.

 

If you reflect back to the interior of the home it will reduce the loss-rate by some amount, if you have a datasheet it's usually there how to compute heat-transfer per hour, most have the spectral breakout.

What's missing in modern architecture is thermal-mass storage as part of the daily cycle, some adobe homes stay cool all summer w/o air-conditioning, this can be engineered.

A good wall system has the weather barrier, insulation, thermal-mass, interior finish.

Existing systems are missing the thermal-mass, calculated by thickness and transmittivity to hold heat-cold long enough to reduce energy inputs, easy to sim nowadays.

My practical solution so far is extra sheetrock for existing homes, insulation doesn't stop heat-transfer, just slows it down, thermal-mass doesn't stop it either but slows it way down to where the temperature differential is never very close to the interior, hence comfort zone is preserved.

My recyled product concept for this is recycled sheetrock with additives to increase it's use this way, and, built in pairs of heat-transfer units that recirculate the ceiling heat back to the floor, last round of thermal expansion looks as if it can be passive.

For new construction my spec is a common cement wall with in most cases a foam insert, standard window & wiring, I add in thermal fluid transfer, and adjust how thick the cement & insulation is to adjust, room-by-room the comfort-zone rating per 30F difference per hour down to not much.

RSS

Featured Forum Discussions

What's the Most Profitable HVAC Job for Your Company?

Started by Wayne Melancon in HVAC. Last reply by Wayne Melancon 15 hours ago. 3 Replies

Lighting replacement - 300 watt LED flood light

Started by Mary Sinkler in General Forum. Last reply by Jan E. Graveamker yesterday. 4 Replies

Glass Block Windows

Started by Ken Kalke in Best Practices. Last reply by Sean Lintow Sr on Saturday. 1 Reply

EZ Green Home is Hiring!

Started by Chloe Chapman in General Forum Jan 5. 0 Replies

Videos

  • Add Videos
  • View All

Latest Activity

Michael Dunseith commented on Kirsten Richnavsky's group Retrotec, Inc
"Congratulations on your new postion. Looking forward to working with you in the near future. Best…"
9 hours ago
Michael Dunseith joined Kirsten Richnavsky's group
9 hours ago
Wayne Melancon replied to Wayne Melancon's discussion What's the Most Profitable HVAC Job for Your Company?
"I'll agree with you there Ken. We'll get shopped by residential when the customer already…"
15 hours ago
Horace Douglas Hunt, Jr. commented on Horace Douglas Hunt, Jr.'s photo
Thumbnail

IMG_3138

"and....this was the best looking spot in the air handler. Seal the unit if you want to have any…"
16 hours ago
Horace Douglas Hunt, Jr. commented on Horace Douglas Hunt, Jr.'s photo
Thumbnail

IMG_3139

"Beginnings of mold....due in some part to leaks in air handler pulling hot humid air from…"
16 hours ago
Horace Douglas Hunt, Jr. posted photos
16 hours ago
Eric Kjelshus replied to Wayne Melancon's discussion What's the Most Profitable HVAC Job for Your Company?
"What is your "Key Performance Indicator" dollar per hour? gross dollar per man day? % of…"
yesterday
Jan E. Graveamker replied to Mary Sinkler's discussion Lighting replacement - 300 watt LED flood light
"Hi Mary, What is the purpose of lighting the backyard ?  Sense of safety, night time…"
yesterday

Home Energy Pros

Welcome to Home Energy Pros – the unique digital community by and for those who work in the home energy performance arena.

Home Energy Pros was founded by the developers of Home Energy Saver Pro (supported by the U.S. Department of Energy) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network. Please honor our Guidelines

© 2017   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service