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Product category: Heating Systems, Controls and Management
News Release from: Vent-Axia | Subject: Driving towards more energy-efficient buildings
Edited by the Buildingtalk Editorial Team on 16 December 2005

Driving towards more energy-efficient
buildings

Vent-Axia's Paul Kilburn assesses the impact of the new Building Regulations Documents F and L.

In the relentless drive for greater energy efficiency in buildings, the latest editions of Building Regulations Documents F and L went 'live' this October, and will begin taking real effect as from 6th April next year That's when planning applications for all new and existing buildings will need to demonstrate compliance with the new requirements

Why the changes? By acknowledging the need for adequate means of ventilation and by specifying ventilation rates for the various occupied spaces within buildings, the original Document F-Means of Ventilation was an important step on the road to a healthier indoor environment.

But it only prescribed minimum standards, and once you moved away from the idea of simple room-by-room extract fans and natural 'trickle' ventilation, it was all too easy to get lost in the 'Alternative Approaches'.

The concept of the Alternative Approaches was intended to cover such techniques as whole-house ventilation and heat recovery, but it was all rather confusing.

As these methods are becoming more mainstream, Document F was needed to give more specific guidance.

What's good about the new Document F is that it takes a 'performance based approach', and encourages best practice.

Document F now also addresses the question of ensuring better indoor air quality by removing and preventing the ingress of gaseous and particulate pollutants, in addition to its original focus on condensation control.

More straightforward.

Each of the ventilation methods is brought into the main body of the Document.

Now 'Continuous mechanical extract', Single Room Heat Recovery Products and 'Wholehouse continuous mechanical supply and extract with heat-recovery' feature alongside 'Background ventilators and intermittent extract fans' and 'Passive stack ventilation'.

All have their place as potentially acceptable solutions - the notable exception being positive input ventilation, which has been removed from contention because of concerns about controllability and 'as-installed' performance, especially in the well-sealed buildings of the future.

The design parameters, in relation to the number and type of fans, floor areas, siting of equipment and even maintenance access, are all explicitly defined for each of the specified systems.

So now it's much easier to work out what's needed for a particular project, and to evaluate product choices in terms of overall cost, system performance and ongoing ease of maintenance.

Joined-up thinking.

There is also clear reference to the requirements of Document L-Conservation of Fuel and Power and an important shift in Document F towards energy efficient ventilation.

The 'General guidance' states that 'consideration should be given to mitigation of ventilation energy use, where applicable, by employing heat recovery devices, efficient types of fan motor and/or energy saving control devices in the ventilation system'.

This in turn points us towards improving building SAP Ratings through the use of these techniques, and shows the joined-up thinking now underlying the Government's Standard Assessment Procedure for the Energy Rating of Buildings, Document F and Document L.

Incidentally, SAP 2006 represents a 20% improvement over SAP 2002.

There is also an implicit link with Building Regulations Document E, which addresses the problem of noise ingress - giving further support to whole-house ventilation, which can deliver the necessary air quality whilst shutting out neighbourhood noise.

The new Documents are undoubtedly a strong endorsement for the leading HVAC manufacturers' work in establishing fan-drive efficiency, precise controllability and heat recovery as key characteristics of their product ranges.

It also points the way ahead in ventilation technology - Energy Saving LoWatt DC motors which more than halve electrical power consumption and confer precise fan speed control, 'intelligent' electronic controls which minimise ventilation extraction rates whilst ensuring high indoor air quality, and heat-recovery systems which save as much as 90% of the indoor warmth that would otherwise be lost through essential ventilation.

The need for close-control.

All this is in the context of ideal buildings with a design air leakage rate of 3 ach at 50 Pa.

This is very airtight, and underlines the need for close-control of ventilation rates.

Taken in relation to the Document L requirement for 10 ach, there's an obvious incentive to include powered heat recovery ventilation to achieve better SAP ratings for well-sealed houses.

Passive stack ventilation, being a 'natural' system, might appear to be an attractive alternative in terms of a SAP rating, but the hard-to-control loss of warm air runs against the energy-saving aims of the Regulations - particularly as motor power is a relatively small component in the overall ventilation energy equation.

And the reality is that such systems will require some sort of powered fan anyway, to provide ventilation in still weather - further compromising their potential SAP advantage.

Heat recovery ventilation also brings electric heating back into the frame - combining the two can produce an 'energy-positive' solution.

For developers of apartment buildings, where electric heating is the most practical option, this is good news.

And it's good news for residential social landlords faced with refurbishment projects featuring large numbers of electrically heated homes - a task made easier if the heat recovery ventilation systems and the replacement electric heaters can all be sourced with a single manufacturer as part of the overall scheme.

As-installed performance.

Perhaps the most significant change for manufacturers relates to the 'as installed' airflow performance of ventilation equipment.

It has long been a bone of contention that solutions featuring minimum spec/minimum cost fans have not been up to the job, despite test performance data suggesting their suitability.

Now Document F calls for airflow performance to be tested to a standard more relevant to actual conditions of use - to this end, the recently published suite of EN 13141standards has been referenced, which gives a closer assessment of true volumetric performance of ventilation products in real installations.

The pay-off.

Far from creating administrative overload for HandV manufacturers and the building industry, the new Documents F and L are doing a great deal to clarify building design requirements and means of compliance.

Previously, Document L called for the best energy-efficient solutions, but Document F didn't offer them.

Now Document F is 'filling the gap' by giving developers, specifiers and contractors practical choices when it comes to ventilation and energy conservation.

It gives true scope for specifiers to set a lead in energy saving, for property managers to improve their building stock, and for developers to add value in an increasingly competitive and energy-aware marketplace.

It all adds up to best practice and better choices.

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