How to Handle HVAC in Extreme Heat?

What is HVAC when it's about?

Building styles need to change in those areas to take advantage of the work the heat can do. For example the sun baking down on the roof of a conventional house will cause the temperatures inside to increase, regardless of how well it is insulated. If a heat reflecting membrane is applied to the surface and then a second roof is installed above, with an airgap open at top and bottom, then a strong ventilation flow will remove the heat when exposed to the sun at no extra cost. the steeper the roof the better it will work.

The same can be done with the exterior walls. Also large overhangs or canopies over the windows should be used on the south side to minimise direct exposure to the sun. Automatic motorised vertical venetian blinds, equipped with a tracking system, can also be installed outside vindows exposed to direct sun. this will reduce the heat load and still let natural light in.

These measures will make it easier for existing systems to cope with the increasing heat loads.

Use a larger condenser.

I doubt that the amount of global warming thus far is enough to call for significant design changes.

100% correct -

Adequate external insulation helps greatly - use R50 above the shell and under the roofing and it helps - I often take a nap in an attic bedroom - in midsummer even on the hottest days here.

Agree--I installed a triple -ply reflective foil, with air pockets between the plies, on the underside of my roof rafters (Living in Los Angeles), and now, even on the hottest days, one can go up, and work in the attic--I also employ 3 attic fans, 2 "pushers", and one large "puller", that are themostatically controlled, to move air out of the attic (Air is brought in from the shaded areas under the eaves through attic vents)--The result is that even on the hottest days, (105 -115 degrees) 3 days in a row, my air conditioner is not needed--When the heat wave lasts for more than 3 days, then the mass of the whole environment, concrete, walls, siding, roof all stay hot, and the air is finally needed . Temp is set at 78 -82, depending on the humidity--Best investment I've made, energy wise.

What about energy costs and security?

Why rely on active technology when smart design of passive systems can reduce costs and increase comfort?

I am guessing you are encouraging more energy use to lead to more potential for extreme weather and tornados? ;) Us humans want to spend less to operate our buildings, and don't take too kindly to your kind ripping our buildings out of the ground... ;)

Passive modifications to existing buildings are limited in value.

Not always - adding window films or shading devices can reduce solar gain - reducing cooling requirements and protecting interior finishes; sometimes it also can help with security / reducing risk of glass breakage in the building. This could save costs on multiple fronts.

Also with windows - for mid to low rise commercial, when replacing/upgrading, better and operable windows also helps in multiple areas.

Roofing membranes can be replaced (or existing covered) with materials with high levels of solar reflection, reducing cooling loads. Insulation is always going to save energy - often in big ways.

Not exactly passive, but changing from exhaust fans to ERVs or HRVs saves energy without adding major costs.

The saying "you are part of the solution or part of the problem" applies. Dismissing energy savings techniques in favour of over sizing equipment is a problem that can be remedied by thinking about how to minimize energy savings. Just routinely oversizing things is a lazy response to a design problem, and is a disservice to clients

I expect I have some experience along this line - in building new homes it is important for sales purposes.

Window films I have used for my home in the past and they can be a big help in preventing solar gain. How they help with security or reduce risk of glass breaking is a bit of a stretch.

Replace windows? - costly and unless one has single pane windows is unlikely to be too big of savings.

Being able to draft air through the space can be great - I have yet to turn on the AC the past three summers we have lived in this home. A breeze off the gulf is wonderful.

Replace a roof - only if it is due to be replaced.

With our concrete structures and mild climate external insulation is a winner.

Fans, ERV or HRV devices are definitely not passive - they are winners but eat up the kWh as well.

Your last statement is a nice bit of sales blather but I do agree that routinely oversizing things is costly and stupid - especially heating and cooling items.

WHY...would a bigger condenser be "wrong"? The HVAC could be partially run with photo-voltaics. On the cheap,the US has many solar-powered vent fans for roofs, available in big-box stores like Lowe's /Home Depot. Some store had R-30 insulation @ 99 cents a sq. ft. With my air off, I survived with weeks of 115 degree heat(--from interior thermostat) with fans/frequent cold showers/cool-water "spritzers". The electric bill dropped to less than half of what it was. The refrigerators acted "stressed." I kept the coils clean and sprayed very dilute alcohol-water mix on the outside, when they were failing and they snapped-back. How expensive is energy in Turkey, compared to the USA?