hot attic solutions

[Carey]

Cat, it would work, but the line would also get sweaty, and drip (much like a dehumidifier, but with no drip pan....and even if you did go... hey & a dehumidifier so install a drip pan system, too! it would be an open system, so you would be dehumidifying the great outdoors, & all of the water would be dripping into the attic drip system, esp when the hot water was running.... way too much to think of!

Plus I really like to reduce the chance of water leaks in the attic... so I have always tried to eliminate attic lines, just more potential for failure... part of this is midwest upbringing... water lines in the attic can freeze, YIKES! Even small stuff leaks can escalate in the attic & ruin walls, & other stuff underneath.

For maintaining a close to ambient temp. room below an attic the most recommended process has been;
1. increase air vents (the less mechanical, the less failure, but mechanical can help... can you increase your non-mechanical vents? Have you looked at your facia/eave level vents, can the free air space on them be increased?.... this is usually one of the least expensive & easiest things to do.... )
2. Install radiant barriers - the goal is to reduce the attic heat, so put it UP, not on the floor of the attic
3 Install insulation - if there is a marked difference in OUTSIDE & inside temp (example: no matter how well insulated a cooler is, after a while it will reach the outside temp... if the attic is hot, even with insulation, the ceiling of the room will be warmer than the wall.)

As long as the attic is heating up, the room below will be warmer than if the attic is at ambient temp.

[Kapohocat]

Yes, we do all those things with our clients already, I was trying to think outside the box... the key you mentioned was the condensation. I hadnt thought of that issue.

We have run most of our plumbing and all the elec above the 15' elevation mark.

[DTisme]

hotinhawaii, point taken. We'll definitely go w/barrier just inside roof first.

[Jay Bondesen]

In central California, 100+ in the summer, a whole-house fan is pretty common. It can go into the ceiling of any room or closet. You open a window, preferably across the house on a shady side, and you draw outside air into the house and out through the attic using existing vent openings. This way you are also bringing fresh air into the house. In CA you would only run it late in the day when it's cooler outside than inside but here you could run it anytime. It is another electric device but it may not need to run very much or often.

Jay

[MarkP]

It's not that radiant heat is this magic thing like X-rays that penetrates everything. Fiberglass insulation will stop radiant heat. The surface of the batt facing the hot roof will get warm and then it is a function of what R-value the fiberglass is as to how hot the rooms below get. What is nice about radiant barriers is that they can be effective (against radiant heat) using only a fraction of the materials of an equivalently effective fiberglass batt. The downside is that they have basically no R-value and are effective ONLY for radiant heat.

[MarkP]

Ceiling fans are great too but they must be used in the right way. Despite the fact that most houses are not designed to maximize thermal mass in the sense that it is often referred to on the internet like stone walls or earth ships, nevertheless there is some thermal mass in every house, and if you are building or remodeling the house you can add an extra layer of sheet rock. It will give you more mass and better sound attenuation and possibly better fire resistance. Anyhoo, run the fan in the evening as soon as the outdoor air is cooler than the indoor air. You will notice a benefit right away, but continue running the fan all night. If you get cold put another blanket on the bed but welcome that cold as it saturates the house. In the morning as the sun rises, turn off the fan. The relative coolness will last a few hours.

I don't think that condensation would form on pipes in Hawaii. I can't recall seeing it happen. The water temp is not that cold particularly if the water has been sitting in an above ground catchment tank and is therefor the same temp as the average air temp. If you are going to that much trouble, put the pipes on the roof not in the attic. That way they will get first crack at the solar heat. Also, add some insulation between the pipes and the roof, maybe flatten the pipes so they catch more sun, and put a clear cover over the pipes so that the rain doesn't cool them off easily. In other words a solar collector. As the solar collector intercepts the sun and heats the water it is shading the roof. The pipe in the attic is a spectacularly inefficient collector having as it does an opaque insulated cover between the sun and the pipe.