Exercises: Bioclimatic architecture and energy saving

Explain what bioclimatic architecture is and name two of its characteristic strategies, stating what each one achieves.

In Mexico, why is it beneficial to face the large windows of a house toward the south? Explain what this achieves in winter and what problem may arise in summer.

The figure shows the cross-section of a bioclimatic house, with a wall feature marked with ?. State what this feature is, what function it serves, and explain why the winter sun enters through the window while the summer sun does not.

Name three renewable energy sources and three non-renewable ones, and explain the fundamental difference between the two groups in one sentence.

Explain what the thermal insulation of a building is and name the two elements of a home where it is usually most important (roof, facades, windows), justifying your choice.

What is the energy label on household appliances? Explain what its letter indicates and why it is worth looking at it (and at the annual consumption figure) before buying.

Explain why a double-glazed window insulates better than a single-glazed one: what role the air gap between the two panes of glass plays.

Name three energy-saving habits at home, estimate which one saves the most energy over a year, and justify your estimate.

A classroom gets very hot in the afternoons during June. Propose three bioclimatic solutions (without air conditioning), order them from lowest to highest cost, and explain how each one works.

Explain what thermal insulation in a building is and reason the meaning behind the phrase "insulation is the first form of heating", relating it to energy demand.

Explain what cross ventilation is, how it is achieved in a home, and why it cools down a space without using electricity.

An apartment gets very hot in summer due to a west-facing window that receives the afternoon sun. Propose three solutions (exterior awning, blind, interior reflective film) and analyze the cost and effectiveness of each, explaining why exterior shading works better.

A $9\ \text{W}$ LED bulb replaces a $60\ \text{W}$ incandescent bulb that gave the same amount of light. If it is turned on for 4 hours a day, calculate how much energy, in $\text{kWh}$, is saved in a year (365 days).

Explain what the "thermal mass" of thick walls is and how traditional houses in northern Mexico take advantage of it to stay cool during the day and warm at night.

A north-facing classroom receives no direct sunlight all year. Is it a bad orientation? Qualify your answer: what advantage does it have for natural light without heating, what uses benefit from it, and what insulation strategy does it require in winter?

Design a school experiment to compare the insulating properties of three materials (cork, wool and polystyrene): setup with identical boxes and hot water or ice, which variable is measured, and how to ensure the test is fair.

A home consumes $1,200\ \text{kWh}$ per year in electric heating (at $0.20\ \text{\$/kWh}$). A company assures them: "If you invest $\$1,800$ in insulating the facade, you will reduce consumption by $40\ \%$ and pay off the work in about $5$ years, because energy prices keep rising."\na) Calculate the annual financial savings with the current rate and determine how many years it would actually take to pay off the investment without price increases.\nb) Refute the 5-year claim with data: what average price would the kWh need to be paid at during that period to pay off the $\$1,800$ in just 5 years? Is it a realistic forecast?\nc) Technically justify whether you would recommend carrying out this work first or whether it would be advisable to prioritize low-cost measures (such as sealing window drafts or programmable thermostats), considering the cost-benefit ratio.

An office building in Madrid has its four facades completely glazed with conventional curtain walls. The owner company proposes installing identical tinted solar films on all the building's glass to solve the heat problem in summer.\na) Refute why applying an identical solution on all four facades is a bioclimatic design mistake, analyzing solar radiation and thermal and lighting needs on the north facade compared to the south facade.\nb) Design a differentiated passive bioclimatic renovation proposal: indicate what type of solar shading (horizontal or vertical) you would install on the south facade and on the east and west facades considering solar altitude, and what thermal or glazing intervention you would prioritize on the north facade. Justify each decision.

Design the bioclimatic strategy for a new classroom in your local area: orientation of windows, overhangs or awnings, insulation and ventilation. Justify each decision based on the climate of your area.

A residential community spends $\$80\,000$ a year on central heating and is considering two investments: insulating the facade ($\$240\,000$, saves $30\ \%$) or replacing the boiler ($\$160\,000$, saves $15\ \%$). Calculate the annual savings and payback period in years for each option, and make a qualified recommendation.

Design the bioclimatic strategy for a public library in Monterrey, where summers are very hot: orientation, solar shading of facades, ventilation and materials. Justify each decision based on the climate.

A school replaces $100$ $60\ \text{W}$ fluorescent luminaires (which operated for $6\ \text{h/day}$) with $20\ \text{W}$ LED panels. An energy saving of $66.7\ \%$ was projected. However, after the renovation, lighting electricity consumption was only reduced by $33.3\ \%$ because the staff, perceiving that "LEDs consume nothing", leave the lights on for an average of $12\ \text{h/day}$.\na) Calculate the original daily consumption in $\text{kWh}$, the projected consumption after installing the LEDs, and the resulting actual consumption. What percentage of the theoretical savings has been lost?\nb) Explain using these data what the "rebound effect" (or Jevons paradox) is and how it distorts energy efficiency forecasts.\nc) Design two automated technical measures (sensors, timers, or control systems) that prevent this rebound effect without relying on the will or behavior of the users.

On a sustainability forum, a user states: "A heat pump with a $\text{COP} = 4$ generates $4\ \text{kWh}$ of heat for every $1\ \text{kWh}$ of electricity consumed. This violates the principle of conservation of energy, as it implies an efficiency of $400\ \%$, which is physically impossible."\na) Technically refute this statement: explain where the remaining energy comes from and why transferring heat is not the same as generating it through the Joule effect.\nb) If a single-family home requires $7,000\ \text{kWh}$ of thermal energy per year for heating, calculate the electricity consumption and the annual bill (at $0.20\ \text{\$/kWh}$) using electric radiators compared to a heat pump with $\text{SCOP} = 3.5$.\nc) Predict what will happen to the instantaneous $\text{COP}$ and the power consumed by the heat pump during a cold snap where the outdoor temperature drops from $10\ ^\circ\text{C}$ to $-5\ ^\circ\text{C}$. Justify your prediction.

A contemporary house built in a dry Mediterranean climate zone features large unprotected west-facing windows and lightweight partition walls. In summer, the interior becomes uninhabitable after 16:00 and the air conditioning units must run at maximum capacity continuously.\na) Identify the two main physical design errors regarding evening solar radiation and the thermal inertia of the building envelope.\nb) Design a renovation proposal inspired by two solutions from traditional vernacular architecture (such as shaded interior courtyards, latticework, or thick walls such as rammed earth). Explain for each one the passive physical principle it harnesses (evaporative cooling, radiation interception with ventilation, or thermal wave lag and damping).