Is Double Glazing Worth the Cost?

Glazing in Schools

MEPS recently performed an exercise on a school classroom block to compare the difference in the heating/cooling power usage between single glazing and double glazing. It was found that the simulated power usage throughout the year dropped by almost 10% with the use of single glazing!

This may sound crazy but let’s look at this closely.

A major component of the cooling load within a space is the solar gain through windows. There is very little difference between the solar gain through double glazing when compared to single glazing. The thermal advantage of double glazing comes from its ability to restrict the conduction of heat between the inside and outside. This is great in winter, but under certain conditions when coupled with high solar gain, this can lead to overheating in summer.

The solar radiation passes freely through the glass and is absorbed as heat by surfaces or objects such as your desk and carpet. This heat is then trapped inside by the glazing and the wall/roof insulation. This is a phenomenon known as the greenhouse effect, commonly used in greenhouses to keep plants warm during the cooler months. However, the superior thermal performance of double glazing used in modern buildings enhances this effect and can cause overheating.

This may not be an issue in spaces which are occupied less during the day, such as a household. However, for spaces such as an office or school, the use of single glazing over double glazing may be beneficial.

We do not want to write off double glazing all together. Double glazing can be used effectively in combination with carefully designed shading to reduce unwanted solar gains during the summer months. There are many factors to consider including the ventilation strategy, shading, thermal mass, window orientation, low-e coatings and tints. Double glazed windows also have condensation and acoustic benefits.

Ask your mechanical engineer to perform an analysis and you may be surprised by the results!

Timber Floor Service Considerations


Timber floor construction for multi story buildings has many advantages but provides a few challenges when it comes to services. Some items to consider when designing with timber floors include:

  1. Where is the fire rating: Fire rated ceilings that are also the finished ceiling require fire rated or surface mounted light fittings and fire rated HVAC grilles/diffusers which are expensive and complicated to install
  2. Joist penetration restrictions: Joists can only be penetrated in a zone in the middle and often require additional flanges for penetrations. This greatly restricts how far the drains can run and may result in more risers being required.
  3. Joist layout vs fixtures above: with less space between joists the locations of fixtures like toilets and shower need to be considered to ensure they do not sit directly above a joist

A good option to combat most of these items is a lower “finished” ceiling under the fire ceiling with sufficient space between to run the services.

Will My Rangehood Work?

RAngehood Ducting length example

It is a requirement of the New Zealand Building Code that spaces in household units, including apartments, that contain cooktops must have mechanical extract that discharges outside. This is typically achieved through a rangehood which are often rated to a maximum “length of duct”.

Some entry level rangehoods may only be rated for as little as 3m by the supplier or even rated to only discharge immediately through the wall they are installed on. This can pose a problem. In modern day apartments it is not unusual for the kitchen to be located 5m or more from the point of discharge!

Duct fittings like a 90° bend may be equivalent to 2m or more of straight duct in the suppliers documentation. A rangehood rated for a maximum “duct length” of 5m could be reduced to only 3m with just one bend! Careful consideration of the duct route and rangehood requirements must be taken when locating the kitchen and oven.  

When choosing a kitchen rangehood it is important to consult with the supplier and the project mechanical engineer for proper pressure drop calculations to confirm whether the rangehood will meet the required performance.

Copper or Plastic Piping: Which is best

Copper Piping

Water Piping – Copper or Plastic

When it comes to water pipes, copper has been the material of choice for a very very long time.

Plastic pipes of all sorts (PEX, uPVC, HDPE) have become increasingly popular in the past 20 to 30 years. One reason being the increasing cost of copper pipes over their equivalent in plastic.

So, what are the pros and cons?


There is no one 100% safe solution. Little is known at present about the plastic piping release of volatile organic compounds (VOC’s) and assimlable organic carbon (AOC’s). Copper is the system with the easiest of issues to control and mitigate and on balance appears to be the better option. 

Mitigating Potential Terrorist Attacks on Buildings

Murrah Federal Building, Oklahoma City, USA.

Terrorism is not an easy or pleasant topic of discussion, but in this day and age, it is a reality that we need to be prepared for, rather than experience the consequences.

As building professionals, it is incumbent upon all of us to at least address the issue when we are engaged in our normal daily design processes. As we hear on the news daily, the enemy is getting more sophisticated with brains running their ill quests for the destruction of humanity. We need to be aware of our own vulnerabilities and potential risk.

There are rules we follow in relation to minimum distance between building fresh air intakes from toilet exhausts, sanitary vent pipes and other sources of objectionable odours. Thanks to dilution, these are not typically life threatening.

But, what if a terrorist released poisonous or radioactive gas into the fresh air intake of a large iconic building with large occupant densities? How safe are these fresh air intakes? Are they secure? Can they be quickly evacuated if detected?

Whilst New Zealand may seem removed from this, we are not immune. As some say ‘An ounce of prevention is worth a pound of cure.’

It is worthy to note that existing buildings with fresh air intakes that are impractical to secure can be protected. This includes the installation of sensor array, capable within milliseconds of detecting chemical, biological and radioactive acts of terrorism. The sensor array can immediately shut down the building ventilation system and sound the fire alarm to evacuate the building.

The above is only one scenario that we need to be considering.

The US Department of Homeland Security has a reference manual to Mitigate Potential Terrorist Attacks Against Buildings. We can assure you this manual is an eye opener and a must read.

Download it here:

Cooling and Heating by Chilled Beams are Here to Stay

Chilled Beams 20141126

Chilled beams is the world’s most recent technique for in-ceiling heating and cooling applications.

Simply based on a horizontal air coil with room air induced over it by a combination of buoyancy and induction air forces, the system’s benefits are;

  • A virtually silent system,
  • No moving parts, no fans,
  • No routine maintenance within the office space,
  • Low ceiling space requirement (about 220 mm),
  • Can be either exposed or ceiling concealed,
  • Most efficient system available,
  • No condensate drainage,
  • Very good zone control capability,
  • Can be installed in a raking ceiling.
  • Can easily substitute conventional 2 or 4 pipe chilled water systems in existing buildings and
  • Now chilled beams are fabricated in New Zealand.

Pacific Consultants (now known as MEPS Building Engineers) have to date completed two projects incorporating chilled beams;

  • Recently, the new Mainfreight Terminal building and offices in Christchurch and
  • The Willis Centre, Wellington. (Merit Award- ACENZ Innovate Awards of Excellence)

Natural Green Pools!

Green Pools

Natural Green Pools is a new trend in the domestic swimming pool industry. Hopefully not due to the dreaded common algae (Pediastrum boryanum).

Whilst a private pool is an asset and a pleasure for the family, many people suffer from allergic reactions to chlorine, normally added to swimming pools as a disinfecting agent.

If you are intending on designing a new pool for your family or for a client, why not consider a natural green pool.

Admittedly, this is not a new idea.

Based on a chemical free natural filtration system, it allows the perimeter water-loving plant beds to act as a water filter and do all the work a typical pool filter would do.

Pool water overflows onto the perimeter plant beds (water restoration area). Water is filtered by absorption through the carefully designed plant bed. Pumped underdrains (acting as subsoil drainage coils but in reverse) the clean and filtered water is then returned to the pool. Simple, no chemicals added!

So, your next natural green pool will require no harmful chemicals, will be fairly low-tech, and once established, it will require little of your time to maintain. Only top up now and then whilst you are drinking a cold minty mojito. Oh, these summer days are coming!

Warranty Conditions of Contract for Fixtures Fittings & Equipment

Pacific Islands

Pacific Consultants (now known as MEPS Building Engineers) are involved in a small number of South Pacific design building projects. Recently we ran into an issue with the warranty conditions of contract for equipment repair during the normal warranty period.

The manufacturer of the equipment had warrantied the equipment for replacement parts only but tagged out time and travel knowing the final destination for the equipment.

The contractor expected the manufacturer to travel to the island and repair the equipment for free.

The situation remained unclear for a few months regarding who was responsible for the repair. It was not until we managed to sight the original sale offer that the situation became clear.

The lesson learned is: whilst most contract documents are implicit on warranties, it pays to stipulate the warranty conditions of contract for replacement parts, travel to site and labour.

LED: Lighting for the Future

2014 LED Lighting

LED lighting technology is fast approaching maturity. We are at a stage where we now specify LED lighting as a matter of course for certain applications.

Today, LED lighting can deliver colour temperatures ranging between 2700K (warm white) to 4000K (cool white) that maintain a very high colour rendering quality that are similar to fluorescent lamps.

Lighting efficiency:  LED light sources  beats all other light sources hands down. Simple comparison courtesy of the European Commission is shown below.

Pricing of LED lamps and fittings have come down substantially. For example at present prices, an LED downlight retails at around $50 compared to $25 per halogen recessed down light. Still double in price but once thermal stability, heat shielding and energy costs are taken into account, overall costs can be demonstrated to be similar at day one and much less in the long run.

2014 LED Lighting Chart

Services Must be Seismically Restrained to Comply with Clause B1 of the NZ Building Code

Seismic Map of NZ

Whilst the seismic restraining of building services is nothing new to the industry, the recent earthquakes in Canterbury have generated new emphasis on the design and installation of seismic restraints in buildings.

The standard that we all have to comply with is NZS 4219:2009. The following are an example of the requirements and stipulations contained within;

Ceiling Supported Equipment

Equipment Within Ceiling Voids: Air diffusers, grilles, and other fittings weighing less than 10 kgs shall be positively fixed to the ceiling. Equipment exceeding 10 kgs in weight must be independently supported of the building structure plus a 25 mm gap between component and ceiling to allow independent movement. Equipment weighing greater than 25 kgs will require specific restraint design.

Light Fittings

Recessed or surface mounted luminaires must be positively fixed to the ceiling T-rail system by way of nuts, bolts or locking clamping devices.

Cable Trays

Cable trays suspended greater than 400 mm from structural support must be seismically restrained. For cable trays not requiring restraint must be installed with a clearance of 150 mm from hangers and braces. Where a cable enters the building, it must be sleeved to allow 25 mm movement is all directions.

Electrical Cabinets

Must have doors fitted with top and bottom catches. Electrical components contained within cabinets must have straps, bars, bolts or similar to provide positive restraint.


Generally pipes less than 50 mm in diameter require no specific seismic design. Similarly, pipes rigidly supported no more than 150 mm from the structure above require no additional support. Pipes that require no seismic support will have to be installed 150 mm from adjacent ceiling hangers, braces and other separately supported equipment. Pipes larger than 200 mm in diameter will be subject to specific seismic support design.

Air Ducts

Rigid ducting with a hanger length greater than 200 mm between the structural support and top of the duct shall require seismic restraint. Interestingly, the Standard stipulates flexible ducts longer than 1.5 m also requiring seismic restraint.

Fans, Fancoil Units etc

Suspended components that are installed in line with duct systems and weigh more than 10 kgs will require to be supported and laterally braced independently of the duct system.


Such as concrete plinths supporting equipment must be reinforced and anchored to the structural slab they are mounted to.

Vibration isolators and resilient mountings

Shall have stoppers or snubbers in each orthogonal horizontal direction and vertical restraint to resist overturning.  Snubbers shall be specifically designed to restrain the seismic forces imposed by the dynamic impact of the component against the snubber.

Tanks and Vessels

Have to be considered as a single mass and restrained against sliding and turning.

Flues and Stacks

Have to be restrained in two perpendicular horizontal directions. Supports shall also be designed to prevent slip joints and other flexible connections from being pulled apart. Flues shall be accessible along their entire length for inspection.

Lifts and Escalators

Refer to NZS 4332:1997 Non-domestic passenger and goods lifts.

Fire Sprinkler Pipework

Refer to NZS 4541:2007 Automatic fire sprinkler systems.

Whilst the above is a condensed summary of Standard 4219:2009, please take the time to refer to it here for additional information and requirements.