02_Useful Energy demand - Causes and Reduction

• Useful energy demand: Amount of energy

  required for heating, cooling, lighting etc.

• Final energy demand: Useful energy demand + plant technology (losses from generation, distribution, storage and transfer of heat) → Extension of the assessment limit towards building boundary

• Primary energy demand: Final energy demand + entire upstream chain (losses from extraction, conversion and transport of the respective energy source) → Extension of the assessment limit towards the energy source

The operative temperature 𝑇𝑜𝑝 describes the perceived temperature and consists mainly of the

room air temperature 𝑇𝐴𝑖𝑟 and the radiation temperature of the enclosing surfaces 𝑇𝑅𝑎𝑑.

• the CO2 concentration indoors should stay below 0,1 - 0,15 % (1000 – 1500 ppm)

• The global average of CO2 in the atmosphereis about 0,041 % (410 ppm)

• Useful temperature: 35 – 45 °C

• but: Permanent problem legionella

• Bacteria typically found in fresh water that can multiply inhotwater pipes

• Infection via inhalation of contaminated aerosols(e.g.during showering)

• Ideal conditions for reproduction: 25 -45 °C, stagnant water

• Die off at ~ 60 °C

• Technical regulations (Germany): < 3L pipe volume (accomplished by hydraulic disconnection -> heat exchangers) or regularly temperatures >= 60°C

• useful energy demand QN = Amount of energy required for heating, cooling, lighting

  etc.

• hot water demand Qw

• space heating demand Qh

• heat demand : Qw + Qh

• in [kW]

• Heating power required to reacha certain temperature

• in [kWh]

• Energy required for heating in ain a certain period of time

• Usually given for a period of one year and area related

Only the user can achieve energy reduction by changing e.g.:

• Domestic hot water temperature and mass flow rate

• amount and switch-on times of appliances

on one hand by the user and on the other hand by various characteristics of the building:

by user:

-> Short intense ventilation (Stoßlüften), night ventilation in summer, Shading, Usage of efficient appliances

building related efficiency potentials

-> everything described here: e.g. Windows, building size and shape

Decreased price leads to increased usage

• Surface-to-Volume ratio

• Zoning

• Windows

• Orientation

• Passive house vs. plus energy house

• Shading

• Lighting, Light directing systems

• usw.

Transmission heat losses of buildings strongly

depend on their surface-to-volume ratio (A/V)

which describes the compactness

• A detached single family home will never be as energy efficient as a duplex or a townhouse building.

• Apartment houses are the most efficient way of living, so we should find a way to make them more attractive, e. g. by offering welcoming community areas and recreational facilities and services nearby

• Placing of similar conditioned rooms next to each other

• Placing of cold/dark rooms on the north side or in the basement

+lighting

+solar gains in winter

+connection to the outside

+escape way

-solar gains in summer

-heat losses in winter

-low surface temperature of glass on cold days

North façade:

• Solar gains through diffuse radiation are small

• Windows have higher U values than insulated walls which leads to tremendous heat losses in winter

South façade:

• Shading is necessary in summer to prevent high indoor temperatures

• Windows to the south maximise solar gains in winter.

• Passive house: maximizing solar gains through windows

• plus energy house: maximizing solar gains through photovoltaics

The zenith angle of the sun changes throughout the year and with it the lighting situation.Shading is necessary to avoid high indoor temperatures in summer. At the same time, there‘s a wish for natural lighting at any time.

Cooling by natural ventilation (open window)

-> no additional energy demand

The heat storage capacity QS of a building depends on the specific heat capacity of the building materials and their masses

• 2nd law of thermodynamics: "Heat always flows from the body of higher temperature to the body of lower temperature

• extensive: textile, substrate < 15cm

• intensive: planters, substrate > 15 cm

cooling in summer:

- shading

- evaporative cooling

thermal insulation in winter

- reduced wind attack

- stagnant air layer

cooling in summer

- shading

- evaporative cooling

thermal insulation in winter

- reduced wind attack

- stagnant air layer

Since there is no cooling or heating needed as well as no ventilation, I would plan the room on the north side or in the basement or next to similar conditioned rooms, because there is no need to heat this room. One can place other parts of the building which have a higher heat demand in the upper floors or on the south side.

• prevents uncotrollen air flow

• increases energy efficiency

• consistent room temperature

The smaller the surface-to-volume-ratio the better the energy efficiency of the building

• heat storage capacity

• insulation material

• night time ventilation

1. building structure

2. location

3. plant species

4. maintenance